diff --git a/docs/integration_guide/non-secure_client_extension_integration_guide.rst b/docs/integration_guide/non-secure_client_extension_integration_guide.rst
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+#############################################
+Non-secure Client Extension Integration Guide
+#############################################
+
+This document introduces TF-M Non-secure Client Extension (NSCE) and how to
+integrate it with Non-secure Processing Environment (NSPE) RTOS.
+
+****************
+What is NSCE for
+****************
+
+Besides the secure services provided via PSA APIs, there are two interactions
+between TF-M and NSPE RTOS.
+
+- Non-secure context management in TF-M
+
+  When a NS task calls a secure service, a context is maintained in TF-M. If
+  TF-M supports multiple secure service calls, the context needs to be loaded
+  and saved with the corresponding NS task when the RTOS kernel (the kernel)
+  does scheduling.
+
+- Non-secure client ID (NSID) management
+
+  As per PSA Firmware Framework specification, NSID is required for a secure
+  service call from the NSPE. The NSID can be managed by either SPM (the same
+  NSID must be used for all connections) or the NSPE RTOS. For the latter case,
+  the NSPE RTOS must provide the NSID for each connection.
+
+NSCE is implemented to support the interactions above.
+
+- Provide the interface to NSPE RTOS for managing the context in TF-M.
+
+- Provide a mechanism to NSPE RTOS for providing the NSID for each connection.
+
+**********************
+NSCE component diagram
+**********************
+
+.. figure:: nsce-integ.svg
+  :align: center
+
+  Non-secure Client Extension Component Diagram
+
+This diagram shows the components of NSCE.
+
+- NSCE interface: The NSCE API interface to NSPE RTOS.
+
+- NS Client Context Manager: It is the internal component of SPM that is used to
+  manage the NS client context. It is not accessible to NSPE.
+
+******************************
+Group-based context management
+******************************
+
+NSCE introduces a group-based context management for NS clients. The purpose is
+to support diverse use scenarios in the IoT world.
+
+For rich-resource devices, TF-M could assign separate contexts for each
+connection. For resource-constrained devices, TF-M may support very limited
+context slots. Multiple NS connections could share the same context provided
+they have mutual exclusion access to the secure services.
+
+To support this flexibility, a group ID (gid) and a thread ID (tid) are
+specified for the connection of the NS client. NSCE allocates only one context
+for a given group. Threads in the same group share the context.
+
+The gid and tid are specified by NSPE RTOS via NSCE interface.
+
+**************
+NSCE interface
+**************
+
+NSCE defines a set of APIs as the interface for NSPE RTOS to manage the context
+in TF-M. NSID is provided as an input parameter of `tfm_nsce_load_ctx()`.
+
+NSCE APIs are typically called by the kernel and must be called from the
+non-secure handler mode.
+
+.. code-block:: c
+
+  uint32_t tfm_nsce_init(uint32_t ctx_requested)
+
+This function should be called before any other NSCE APIs below to do non-secure
+context intialization in NSCE for the calling NS entity. `ctx_requested` is the
+number of the contexts requested by the NS entity. The number of assigned
+context will be returned. It may be equal to or smaller than the equested
+context number based on the current available resource in TF-M. If
+`ctx_requested` is `0`, then the maximum available context number will be
+assigned and returned. If the initialization is failed, `0` should be returned.
+
+.. Note::
+  As TF-M only supports one context for now, so the return value is always `1`
+  if no error. Currently, it is safe to skip calling `tfm_nsce_init()`.
+  But, for future compatibility, it is recommended to do so.
+
+.. code-block:: c
+
+  uint32_t tfm_nsce_acquire_ctx(uint8_t group_id, uint8_t thread_id)
+
+This function allocates a context for the NS client connection. The `gid` and
+`tid` are the input paramemters. A token will be returned to the NSPE if TF-M
+has an available context slot. Otherwise, `TFM_NS_CLIENT_INVALID_TOKEN` is
+returned.
+It is the responsibility of NSPE RTOS to assign gid and tid for each NS client.
+
+.. code-block:: c
+
+  uint32_t tfm_nsce_release_ctx(uint32_t token)
+
+This function tries to release the context which was retrieved by
+`tfm_nsce_acquire_ctx()`. As the context may be shared with other threads
+within the same group, the context is only freed and back to the available
+context pool after all threads in the same group release the context.
+
+.. code-block:: c
+
+  uint32_t tfm_nsce_load_ctx(uint32_t token, int32_t nsid)
+
+This function should be called when NSPE RTOS schedules in a NS client. `token`
+is returned by `tfm_nsce_acquire_ctx()`. `nsid` is the non-secure client ID
+used for the following PSA service calls.
+
+The assignment of NSID is managed by the NSPE RTOS. It is not required to use
+the same NSID for a NS client when calling this function each time. This allows
+the NS client changing its NSID in the lifecycle. For example, the provisioning
+task may need to switch NSID to provision the keys for different NS clients
+created afterwards.
+
+.. code-block:: c
+
+  uint32_t tfm_nsce_save_ctx(uint32_t token)
+
+This function should be called when NSPE RTOS schedules out a NS client. The
+input parameter `token` is returned by `tfm_nsce_acquire_ctx()`.
+After the context is saved, no secure service call can be made from NSPE until a
+context is loaded via `tfm_nsce_load_ctx()`.
+
+**********************
+NSCE integration guide
+**********************
+
+Enable NSCE in TF-M
+===================
+
+To enable NSCE in TF-M, set the build flag `TFM_NS_MANAGE_NSID` to `ON` (default
+`OFF`).
+
+.. _Support NSCE in an RTOS:
+
+Support NSCE in an RTOS
+=======================
+
+For supporting NSCE in an RTOS, the integrator needs to do the following major
+work:
+
+- Integrate the NSCE API calls into the NS task lifecycle. For example,
+  creating/scheduling/destroying a NS task.
+
+- Manage the assignment for `gid`, `tid` and NSID.
+
+The typical steps are listed below:
+
+- Before programming, the integrator should plan the group assignment for
+  the NS tasks that need to call secure services. If the number of tasks is less
+  than or equal to TF-M non-secure context slots, then different gid can be
+  assigned to each task for taking dedicated context in TF-M.
+  Otherwise, the integrator need to think about grouping the tasks to share the
+  context.
+
+- In the kernel initialization stage, it calls `tfm_nsce_init()` with
+  requested context number to initialize the non-secure context in TF-M. The
+  actual allocated context number will be returned. `0` means initialization
+  failed. The kernel could use different group assignment sets according to the
+  context number allocated to it. TF-M only supports one context for now.
+
+- The kernel calls `tfm_nsce_acquire_ctx()` when creating a new task. This
+  should be done before the new task calls any secure service. A valid token
+  returned should be saved as part of the task context in NSPE RTOS.
+
+- When the kernel schedules in a task with a valid `token` associated,
+  `tfm_nsce_load_ctx()` should be called before resuming the execution of that
+  task. The NSID is specified by the kernel through the `nsid` parameter.
+  The mapping between NSID and task is managed by the kernel.
+  `tfm_nsce_load_ctx()` can be called multiple times without calling
+  `tfm_nsce_save_ctx()` for switching the NSID for the same task (same tid and
+  gid).
+
+- `tfm_nsce_save_ctx()` should be called if the current task has a valid
+  `token` before being switched to another task. Calling `tfm_nsce_load_ctx()`
+  for another task before saving the current context may result in NS context
+  lost in TF-M for the running task.
+
+- When the task is terminated, destroyed or crashed, the kernel should call
+  `tfm_nsce_release_ctx` to make sure the associated resource is back to the
+  pool in TF-M.
+
+Integration example
+===================
+
+.. figure:: nsce-rtos-example.svg
+  :align: center
+
+  RTOS/NSCE integration example
+
+This is the software module diagram of a typical RTOS/NSCE integration example.
+
+- Built-in Secure Context Manager: An RTOS may have an existing built-in secure
+  context manager with a group of secure context management APIs defined. Let's
+  take RTX which uses `Armv8-M TrustZone APIs <https://www.keil.com/pack/doc/CMSIS/Core/html/group__context__trustzone__functions.html>`_
+  as the example.
+
+.. Note::
+  RTOS may define the NS task context in the secure side as "secure context". It
+  is the same thing as the "non-secure context" (context for a secure service
+  call from NS client) from TF-M's point of view.
+
+- Shim Layer/Secure Context Manager: If the RTOS has a "Built-in Secure Context
+  Manager", then a shim layer should be provided to translate the built-in API
+  calls into the NSCE API calls. A reference shim layer for RTX TrustZone APIs
+  is `here <https://review.trustedfirmware.org/c/TF-M/tf-m-tests/+/11291>`_.
+
+  If the RTOS has no existing one, then a "Secure Context Manager" should be
+  implemented based on the NSCE APIs. You can refer to the shim layer example
+  above for the implementation. The timing of calling NSCE APIs in the kernel is
+  introduced in the :ref:`Support NSCE in an RTOS` section above.
+
+- NSID Manager: If NSPE RTOS manages the NSID, then this module is used by the
+  secure context manager or shim layer to manage the NSID assignment for the
+  NS tasks. The assignment is implementation defined. A `task name based NSID
+  manager <https://review.trustedfirmware.org/c/TF-M/tf-m-tests/+/11290>`_ is \
+  provided as a reference.
+
+Integration notes
+=================
+
+- `gid`: It is a `uint8_t` value (valid range is 0 - 255). So, maximum 256
+  groups (NSCE context slots) are supported by the NSCE interface.
+  TF-M only supports single context for now. So, it is recommended to use
+  single group ID at this stage.
+
+- `tid`: It is a `uint8_t` value (valid range is 0 - 255). Thread ID is used to
+  identify a NS client within a given group. `tid` has no special meaning for
+  TF-M. So, usually the kernel only needs to ensure a NS task has a unique `tid`
+  within a group.
+
+- `gid` and `tid` management: It is the responsibility of NSPE RTOS to manage
+  the assignment of `gid` and `tid`. Based on the explaination above, the `gid`
+  could be assigned as a constant value. And, the `tid` can be increased
+  globally when calling `tfm_nsce_acquire_ctx()` for a new task. Just notice
+  `tid` may overflow.
+
+- NSID management: It is the responsibility of NSPE RTOS to manage the
+  assignment of the NSID for each task. It is highly recommended that a NS
+  client uses the same NSID following a reboot or update. The binding of a NS
+  client to a specific NSID will ensure the correct access to the assets. For
+  example, the data saved in the protected storage.
+
+- Integrate with the existing secure context management APIs of NSPE RTOS: The
+  NSCE APIs are designed to be compatible with most known existing secure
+  context management APIs. A shim layer is needed to translate the API calls.
+  See the integration example above.
+
+- `tfm_nsce_acquire_ctx()` must be called before calling
+  `tfm_nsce_load_ctx()`, `tfm_nsce_save_ctx()` or `tfm_nsce_release_ctx()`.
+
+- `tfm_nsce_release_ctx()` can be called without calling `tfm_nsce_save_ctx()`
+  ahead.
+
+--------------
+
+*Copyright (c) 2021, Arm Limited. All rights reserved.*
diff --git a/docs/integration_guide/nsce-integ.svg b/docs/integration_guide/nsce-integ.svg
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font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;"><h4>Privileged</h4></div></div></div></foreignObject><text x="29" y="184" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">Privil...</text></switch></g><rect x="459" y="50" width="120" height="60" rx="9" ry="9" fill="#d5e8d4" stroke="#82b366" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 118px; height: 1px; padding-top: 80px; margin-left: 460px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;">Secure Partition</div></div></div></foreignObject><text x="519" y="84" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">Secure Partition</text></switch></g></g><switch><g requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"/><a transform="translate(0,-5)" xlink:href="https://www.diagrams.net/doc/faq/svg-export-text-problems" target="_blank"><text text-anchor="middle" font-size="10px" x="50%" y="100%">Viewer does not support full SVG 1.1</text></a></switch></svg>
\ No newline at end of file
diff --git a/docs/integration_guide/nsce-rtos-example.svg b/docs/integration_guide/nsce-rtos-example.svg
new file mode 100644
index 0000000..906f997
--- /dev/null
+++ b/docs/integration_guide/nsce-rtos-example.svg
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Do not edit this file with editors other than diagrams.net -->
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align-items: unsafe flex-end; justify-content: unsafe center; width: 348px; height: 1px; padding-top: 347px; margin-left: 21px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;"><h3>RTOS Kernel</h3></div></div></div></foreignObject><text x="195" y="347" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">RTOS Kernel</text></switch></g><rect x="471" y="273" width="100" height="40" fill="#f5f5f5" stroke="#666666" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; 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align-items: unsafe center; justify-content: unsafe center; width: 38px; height: 1px; padding-top: 25px; margin-left: 152px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;"><h2>NSPE</h2></div></div></div></foreignObject><text x="171" y="29" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">NSPE</text></switch></g><rect x="501" y="15" width="40" height="20" fill="none" stroke="none" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 38px; height: 1px; padding-top: 25px; margin-left: 502px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;"><h2>SPE</h2></div></div></div></foreignObject><text x="521" y="29" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">SPE</text></switch></g><rect x="16" y="130" width="40" height="20" fill="none" stroke="none" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 38px; height: 1px; padding-top: 140px; margin-left: 17px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;"><h4>Unprivileged</h4></div></div></div></foreignObject><text x="36" y="144" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">Unpriv...</text></switch></g><rect x="11" y="170" width="40" height="20" fill="none" stroke="none" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 38px; height: 1px; padding-top: 180px; margin-left: 12px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;"><h4>Privileged</h4></div></div></div></foreignObject><text x="31" y="184" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">Privil...</text></switch></g><rect x="461" y="60" width="120" height="60" rx="9" ry="9" fill="#d5e8d4" stroke="#82b366" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 118px; height: 1px; padding-top: 90px; margin-left: 462px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;">Secure Partition</div></div></div></foreignObject><text x="521" y="94" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">Secure Partition</text></switch></g><rect x="51" y="275" width="100" height="40" fill="#e1d5e7" stroke="#9673a6" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 98px; height: 1px; padding-top: 295px; margin-left: 52px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;">NSID Manager</div></div></div></foreignObject><text x="101" y="299" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">NSID Manager</text></switch></g><rect x="230" y="270" width="120" height="45" fill="#e1d5e7" stroke="#9673a6" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 118px; height: 1px; padding-top: 293px; margin-left: 231px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;">Shim Layer/Secure Context Manager</div></div></div></foreignObject><text x="290" y="296" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">Shim Layer/Secure Co...</text></switch></g><path d="M 351.5 300 L 351.5 290 L 452.07 290 L 452.07 284 L 470.5 295 L 452.07 306 L 452.07 300 Z" fill="none" stroke="#000000" stroke-linejoin="round" stroke-miterlimit="10" pointer-events="all"/><path d="M 287.5 235.5 L 299.5 235.5 L 299.5 252.07 L 306.5 252.07 L 293.5 272.5 L 280.5 252.07 L 287.5 252.07 Z" fill="#ffe6cc" stroke="#d79b00" stroke-width="3" stroke-linejoin="round" stroke-miterlimit="10" stroke-dasharray="9 9" pointer-events="all"/><path d="M 228.5 290 L 228.5 300 L 168.93 300 L 168.93 306 L 150.5 295 L 168.93 284 L 168.93 290 Z" fill="none" stroke="#000000" stroke-linejoin="round" stroke-miterlimit="10" pointer-events="all"/><rect x="226" y="194" width="130" height="40" fill="#ffe6cc" stroke="#d79b00" stroke-width="3" stroke-dasharray="9 9" pointer-events="all"/><g transform="translate(-0.5 -0.5)"><switch><foreignObject pointer-events="none" width="100%" height="100%" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility" style="overflow: visible; text-align: left;"><div xmlns="http://www.w3.org/1999/xhtml" style="display: flex; align-items: unsafe center; justify-content: unsafe center; width: 128px; height: 1px; padding-top: 214px; margin-left: 227px;"><div style="box-sizing: border-box; font-size: 0px; text-align: center;"><div style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; pointer-events: all; white-space: normal; overflow-wrap: normal;">Built-in Secure Context Manager</div></div></div></foreignObject><text x="291" y="218" fill="#000000" font-family="Helvetica" font-size="12px" text-anchor="middle">Built-in Secure Conte...</text></switch></g></g><switch><g requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"/><a transform="translate(0,-5)" xlink:href="https://www.diagrams.net/doc/faq/svg-export-text-problems" target="_blank"><text text-anchor="middle" font-size="10px" x="50%" y="100%">Viewer does not support full SVG 1.1</text></a></switch></svg>
\ No newline at end of file
diff --git a/docs/integration_guide/os_migration_guide_armv8m.rst b/docs/integration_guide/os_migration_guide_armv8m.rst
index a3b5806..4ef76ae 100644
--- a/docs/integration_guide/os_migration_guide_armv8m.rst
+++ b/docs/integration_guide/os_migration_guide_armv8m.rst
@@ -17,25 +17,8 @@
 - If the OS manipulates directly the Link Register, the default Link Register
   value used in Handler mode transitions needs to be differentiated between
   Secure and Non Secure builds, i.e. ``0xFD`` and ``0xBC``, respectively.
-- If the OS supports the Thread Context Management for Armv8-M TrustZone APIs,
-  as described
-  `here <https://www.keil.com/pack/doc/CMSIS/Core/html/group__context__trustzone__functions.html>`__
-  , and would like to use the non-secure client identification feature of TF-M,
-  then it also have to use the
-  ``enum tfm_status_e tfm_register_client_id (int32_t ns_client_id)``
-  API function provided by TF-M, as described in
-  :doc:`NS client identification documentation </docs/technical_references/design_docs/tfm_ns_client_identification>`.
-- if the OS doesn't support the API mentioned above, it should set
-  ``TFM_NS_CLIENT_IDENTIFICATION`` to ``OFF`` in the cmake system.
-- .. Note::
-
-    This is NOT REQUIRED when the Non Secure OS build is meant
-    to be integrated with TF-M running in Secure world.
-
-  If generic function calls into Secure world have to be supported in Non Secure
-  builds, integrate an API for secure stack memory management (e.g. the
-  TrustZone API for secure stack memory management described in
-  ``tz_context.h``).
+- If the OS manages the non-secure client identification, pelase check the
+  :doc:`Non-secure Client Extension Integration Guide </docs/integration_guide/non-secure_client_extension_integration_guide>`.
 
 --------------
 
diff --git a/docs/integration_guide/services/tfm_ps_integration_guide.rst b/docs/integration_guide/services/tfm_ps_integration_guide.rst
index 50c83a4..c5bb8ac 100644
--- a/docs/integration_guide/services/tfm_ps_integration_guide.rst
+++ b/docs/integration_guide/services/tfm_ps_integration_guide.rst
@@ -293,7 +293,7 @@
 processing environment. It provides a dedicated API to retrieve the client ID
 which performs the service request.
 
-:doc:`NS client identification documentation </docs/technical_references/design_docs/tfm_ns_client_identification>`
+:doc:`Non-secure Client Extension Integration Guide </docs/integration_guide/non-secure_client_extension_integration_guide>`
 provides further details on how client identification works.
 
 PS service uses that TF-M core API to retrieve the client ID and associate it
diff --git a/docs/integration_guide/tfm_integration_guide.rst b/docs/integration_guide/tfm_integration_guide.rst
index f0f2a1e..52156c46 100644
--- a/docs/integration_guide/tfm_integration_guide.rst
+++ b/docs/integration_guide/tfm_integration_guide.rst
@@ -134,8 +134,13 @@
 
 NS client Identification
 ========================
-See
-:doc:`ns client identification documentation </docs/technical_references/design_docs/tfm_ns_client_identification>`.
+
+The NS client identification (NSID) is specified by either SPM or NSPE RTOS.
+If SPM manages the NSID (default option), then the same NSID (-1) will be used
+for all connections from NS clients.
+For the case that NSPE RTOS manages the NSID and/or different NSIDs should be
+used for different NS clients. See
+:doc:`Non-secure Client Extension Integration Guide </docs/integration_guide/non-secure_client_extension_integration_guide>`.
 
 *********************
 Non-secure interrupts
diff --git a/docs/technical_references/design_docs/tfm_non_secure_client_management.rst b/docs/technical_references/design_docs/tfm_non_secure_client_management.rst
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-############################
-Non-secure Client Management
-############################
-
-:Author: Miklos Balint
-:Organization: Arm Limited
-:Contact: Miklos Balint <miklos.balint@arm.com>
-
-***********
-Terminology
-***********
-
-**Secure service call**: request to a secure partition by a secure or non-secure
-client thread
-
-**Secure function call**: any function call from NSPE to SPE
-
-**TrustZone (TZ) API**: the set of functions defined by CMSIS for RTOS secure
-context management
-
-**Client ID**: the identifier defining a single entity within the system,
-determining its access policies for any given secure assets
-
-*************************
-Assumptions, restrictions
-*************************
-
-This design considers as its baseline the current operation of TF-M: an
-operating mode where at any given time only a single non-secure access is
-permitted to call a secure service.
-
-If a non-secure RTOS/bare-metal application does not use the API calls defined
-in this design, that non-secure application is still able to use secure services
-using a single, default non-secure client context. That remains a supported use
-case and use of this API is optional and is only needed if multiple access
-policies and/or concurrent secure contexts initiated by non-secure threads are
-required.
-
-Investigation is ongoing to address the option of enabling multiple concurrent
-calls by non-secure threads without the use of the context management API below.
-
-******
-Issues
-******
-
-The topics being discussed in this document:
-
-- NS client/thread awareness in TF-M Core
-- "Known client" list
-
-Improvements, alternatives, investigations
-
-- Concurrent secure service requests
-- NS to S priority inheritance
-- NS privilege to be derived from CONTROL_NS register
-
-**************
-Design details
-**************
-
-NS thread awareness in TF-M Core
-================================
-
-Description
------------
-
-TrustZone context management API defines a set of secure function calls from NS
-RTOS handler mode to TF-M Core to get notification of context switch.
-
-While CMSIS context management can be used to directly expose secure context
-management to the non-secure OS, TF-M has a proprietary implementation: the
-context management API is used to get notification of NS context switches and
-to track various non-secure clients.
-
-.. _`API definition`:
-
-API definition
---------------
-
-TZ_MemoryId_t data type
-^^^^^^^^^^^^^^^^^^^^^^^
-
-TZ Memory ID identifies an allocated memory slot.
-
-**TF-M usage**
-
-``TZ_MemoryId_t`` is used for an index into an array containing active NS client
-IDs. The memory ID is required by CMSIS to be a positive integer, so it is
-mapped to the array index by being decremented by 1.
-
-**Signature**
-
-.. code-block:: c
-
-    typedef uint32_t TZ_MemoryId_t;
-
-Context management initialization: TZ_InitContextSystem_S
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Initialize secure context memory system.
-
-**Return value**
-
-This function returns execution status: 1 for success, 0 for error.
-
-**TF-M usage**
-
-This function call is used to identify a non-secure RTOS that has TZ context
-management capabilities, as this function is expected to be called before any
-other TZ API function is used.
-
-**Signature**
-
-.. code-block:: c
-
-    uint32_t TZ_InitContextSystem_S (void);
-
-Context allocation: TZ_AllocModuleContext_S
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Allocate context memory for calling secure software modules in TrustZone.
-
-**Parameters**
-
-``module`` [input]: identifies software modules called from non-secure mode
-
-**Return value**
-
-``value != 0`` TrustZone memory slot identifier
-``value == 0`` no memory available or internal error
-
-**TF-M usage**
-
-This function is used to identify a new non-secure thread that may be identified
-as a client in the non-secure domain. The ``module`` parameter is unused. The
-returned ``TZ_MemoryId_t`` value is the index in the ``NsClientIdList`` array
-where the client ID for the newly allocated context is stored.
-
-**Signature**
-
-.. code-block:: c
-
-    TZ_MemoryId_t TZ_AllocModuleContext_S (TZ_ModuleId_t module);
-
-Context freeing: TZ_FreeModuleContext_S
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Free context memory that was previously allocated with TZ_AllocModuleContext_S
-
-**Parameters**
-
-``id`` [input]: TrustZone memory slot identifier
-
-**Return value**
-
-Execution status (1: success, 0: error)
-
-**TF-M usage**
-
-This function indicates that a non-secure client is inactive, meaning that any
-subsequent references to the client ID are considered erroneous. In effect, the
-client ID indexed by ``(id – 1)`` is cleared and the memory slot flagged as
-free.
-
-**Signature**
-
-.. code-block:: c
-
-    uint32_t TZ_FreeModuleContext_S (TZ_MemoryId_t id);
-
-Context activation: TZ_LoadContext_S
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Load secure context (called on RTOS thread context switch)
-
-**Parameters**
-
-``id`` [input]: TrustZone memory slot identifier
-
-**Return value**
-
-Execution status (1: success, 0: error)
-
-**TF-M usage**
-
-The client ID indexed by ``(id – 1)`` becomes the active NS client. Any
-subsequent secure service requests coming from non-secure domain will be
-associated with this client ID.
-
-**Signature**
-
-.. code-block:: c
-
-    uint32_t TZ_LoadContext_S (TZ_MemoryId_t id);
-
-Context deactivation: TZ_StoreContext_S
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Store secure context (called on RTOS thread context switch)
-
-**Parameters**
-
-``id`` [input]: TrustZone memory slot identifier
-
-**Return value**
-
-Execution status (1: success, 0: error)
-
-**TF-M usage**
-
-The client ID indexed by ``(id – 1)`` becomes inactive. Any subsequent secure
-service requests coming from non-secure domain will be invalid until a new NS
-context is loaded.
-
-**Signature**
-
-.. code-block:: c
-
-    uint32_t TZ_StoreContext_S (TZ_MemoryId_t id);
-
-Security implications (to be assessed separately if needed)
------------------------------------------------------------
-
-If NS RTOS / NS handler mode is compromised, NS clients’ data can be disclosed
-to unauthorised non-secure actors, as it’s not in the scope of TF-M to guarantee
-non-secure client isolation. Support for this API is only an enabler for a
-non-secure RTOS feature.
-
-Vulnerabilities of the NS handler mode cannot and will not lead to disclosure of
-assets owned by secure entities to non-secure actors after the introduction of
-this feature as a malicious NS handler can only ever assume the identity of
-another non-secure client and cannot elevate its access privileges to those of
-secure clients.
-
-Known client list
-=================
-
-Description
------------
-
-A different – but related – API to that defined by CMSIS is proposed in this
-design to register a specific client ID to the active non-secure thread.
-
-The purpose of this API is to provide non-secure privileged code with the
-ability to associate the active non-secure context with a pre-defined identity.
-This enables the application of a pre-set access policy on the secure side to be
-applied to the non-secure thread.
-
-Use cases
----------
-
-It is valid for non-secure privileged code to only support the TF-M-specific API
-defined below and not the CMSIS TZ API defined previously. In this case the
-single non-secure client is still able to access resources based on a
-pre-defined access policy in secure services without relying on the default
-non-secure identity configured in TF-M.
-
-If used in conjunction with the TZ API, this function can provide a means to
-assign and identify multiple non-secure client IDs based on the active context,
-overriding TF-M’s default non-secure client identity assignment policy.
-
-API definition
---------------
-
-NS RTOS client registration API – secure function calls from NS handler mode to
-TF-M Core to associate a “known” Client ID to the active non-secure thread.
-
-Register specific client ID: ``tfm_register_client_id``
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Assign client ID to the current TZ context.
-
-**Note**: This function must be called from handler mode so that TF-M can verify
-that it was sent by a privileged entity.
-
-This function call must follow all TZ_AllocModuleContext_S function calls to
-override the default NS client IDs allocated by TF-M.
-
-Secure and non-secure client IDs are allocated from different ranges (negative
-IDs for non-secure clients, positive for secure clients). The function call is
-rejected if called with a secure ID.
-
-**Parameters**
-
-``ns_client_id`` [input]: The client ID to be assigned to the current context
-
-**Return value**
-
-``TFM_SUCCESS`` (0) if the client ID assigned successfully, a non-zero error
-code in case of error.
-
-**Signature**
-
-.. code-block:: c
-
-    enum tfm_status_e tfm_register_client_id (int32_t ns_client_id);
-
-********************
-Implementation notes
-********************
-
-Option to reduce required context switch notifications
-======================================================
-
-According to TrustZone API definition ``TZ_StoreContext_S()`` is to be called
-"at thread context switch after running a thread" and ``TZ_LoadContext_S`` "at
-thread context switch before running a thread". The API definition does not
-define the course of action to be taken if two ``TZ_LoadContext_S()`` calls are
-made without an interleaving StoreContext.
-
-The proposal for TF-M is to accept this as a valid scenario where the second
-``TZ_LoadContext_S()`` call is taken to imply a ``TZ_StoreContext_S()`` with
-the previous active Memory_Id.
-
-This assumption does not alter the intended use of ``TZ_StoreContext_S()``,
-which remains a valid call with the behaviour as defined in the
-`API definition`_ section above.
-
-******************************************
-Investigations, improvements, alternatives
-******************************************
-
-Concurrent secure service requests
-==================================
-
-If there are concurrent services requests, TF-M needs to identify the client for
-each request and should make their corresponding context available in the secure
-domain. Client ID needs to be associated with the secure service request so that
-a NS context switch does not break client identification.
-
-If a non-secure client is blocked on an asynchronous secure service completion,
-the NS TFM library must provide a semaphore the NS thread can wait on, whereby
-NS RTOS can schedule a different context.
-
-Should a secure service completion happen for an inactive NS context, a
-notification mechanism needs to be created to activate the given NS context.
-
-The proposal is for the NS TFM library to include a NS IRQ handler for a
-reserved interrupt signal. The ISR would identify the context to be activated
-and release the corresponding semaphore.
-
-NS to S priority inheritance
-============================
-
-Whether or not NS thread priorities should be influencing secure service
-prioritization needs to be analysed. It is raised as a topic of discussion and
-is not detailed in this document further at this stage.
-
-NS privilege check for secure function calls
-============================================
-
-Non-secure privilege can be derived from CONTROL_NS instead of requiring NS to
-call context management veneers in handler mode. This can be a more generic
-approach, but implications are to be investigated.
-
-**********
-References
-**********
-
-Description of the TZ API:
-https://www.keil.com/pack/doc/CMSIS/Core/html/group__context__trustzone__functions.html
-
---------------
-
-*Copyright (c) 2019-2021, Arm Limited. All rights reserved.*
diff --git a/docs/technical_references/design_docs/tfm_ns_client_identification.rst b/docs/technical_references/design_docs/tfm_ns_client_identification.rst
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-###########################
-Non-Secure Identity Manager
-###########################
-The ID of the current application/thread is known by TF-M, and the PS service
-queries the ID of the currently running client via a dedicated API.
-
-The identity of secure clients can be tracked by TF-M core, because it also
-manages the contexts of the partitions. However to differentiate NS clients, it
-relies on the services provided by the NS OS.
-
-Tracking of context changes are possible by relying on the NS OS calling the
-Thread Context Management for Armv8-M TrustZone APIs, as described
-`here <https://www.keil.com/pack/doc/CMSIS/Core/html/group__context__trustzone__functions.html>`__
-
-However TF-M needs an extra API, to assign a client ID to the TZ context created
-as a result of the
-``TZ_MemoryId_t TZ_AllocModuleContext_S (TZ_ModuleId_t module)`` call.
-See ``interface/include/ext/tz_context.h`` for details of API declarations.
-
-In case the NS OS doesn't use the Thread Context Management for Armv8-M
-TrustZone APIs, then TF-M considers the NS SW as a single client, and assigns a
-client ID to it automatically.
-
---------------
-
-*Copyright (c) 2018-2021, Arm Limited. All rights reserved.*