diff --git a/docs/tfm_test_partitions_addition.rst b/docs/tfm_test_partitions_addition.rst
new file mode 100644
index 0000000..6fec8e7
--- /dev/null
+++ b/docs/tfm_test_partitions_addition.rst
@@ -0,0 +1,88 @@
+######################################
+Adding partitions for regression tests
+######################################
+
+************
+Introduction
+************
+
+Some test group may need specific test services. These test services may support
+one or more groups thus developers shall determine the proper test scope.
+Currently, TF-M test services are located under ``tf-m-tests/test/secure_fw``.
+
++---------------------------------------+---------------------------------------------------------------+
+| Folder name                           | Description                                                   |
++=======================================+===============================================================+
+| test/secure_fw/suites/<suite>/service | Test service divided into corresponding suite subdirectories. |
++---------------------------------------+---------------------------------------------------------------+
+| test/secure_fw/common_test_services   | Common test services.                                         |
++---------------------------------------+---------------------------------------------------------------+
+
+**************
+Implementation
+**************
+
+Adding a test partiton to provide test services is same as adding a secure
+partition, generally the process can be referenced from the document
+`Adding Secure Partition <https://tf-m-user-guide.trustedfirmware.org/integration_guide/services/tfm_secure_partition_addition.html>`_.
+
+Test Partition Specific Manifest Attributes
+===========================================
+
+Each test service must have resource requirements declared in a manifest file,
+the contents of test services are the same as secure partitions, but their
+locations are different. Test service manifests shall be set in
+``tf-m-tests/test/secure_fw/tfm_test_manifest_list.yaml``.
+
+There are some test purpose attributes in Secure Partition manifests that are
+**NOT** compatible with FF-M.
+They should be used in Test Partitions only.
+
+weak_dependencies
+-----------------
+A TF-M regression test Partition calls other RoT services for test. But it
+can still run other tests if some of the RoT services are disabled.
+TF-M defines a ``"weak_dependencies"`` attribute in partition manifests of
+regression test partitions to describe test service access to other RoT
+services. It *shall* be only used for TF-M regression test services.
+
+model
+-----
+A TF-M regression test Partition may support both the SFN and IPC model.
+The actual model being used follows the SPM backend enabled.
+
+The TF-M build system supports this by allowing Secure Partitions to set
+the ``model`` attribute to ``dual``.
+The manifest tool will then change it to the corresponding value according
+to the current backend selected.
+
+The Test Partitions use the following definitions to know what model is being
+built:
+
+- ``<<partition_name>>_MODEL_IPC``, ``1`` if IPC model is used.
+- ``<<partition_name>>_MODEL_SFN``, ``1`` if SFN model is used.
+
+Test service implementation
+===========================
+
+Test service of individual test
+-------------------------------
+
+An individual test dedicated test service should be put under the corresponding
+test folder ``test/secure_fw/suites/<test_name>``.
+
+``add_subdirectory(suites/<test_name>/<service_dir>)`` shall be added into
+``tf-m-tests/test/secure_fw/secure_tests.cmake`` to make sure that the test
+service is built with secure side configuration.
+
+Common test service
+-------------------
+
+If a new test service is required by multiple test suites, the code should be
+put under ``test/secure_fw/common_test_services``. If the new test suite relies
+on a common test service, please make sure that the build implementation of the
+test service is linked correctly, including the header files and libraries.
+
+--------------
+
+*Copyright (c) 2022, Arm Limited. All rights reserved.*
diff --git a/docs/tfm_test_suites_addition.rst b/docs/tfm_test_suites_addition.rst
new file mode 100644
index 0000000..aaf0cdb
--- /dev/null
+++ b/docs/tfm_test_suites_addition.rst
@@ -0,0 +1,438 @@
+#################################
+Adding TF-M Regression Test Suite
+#################################
+
+.. contents:: Table of Contents
+
+*************************************
+Introduction of TF-M regression tests
+*************************************
+
+TF-M regression tests test whether changes to TF-M code work as expected.
+A new regression test can consist of following 3 components:
+
+1. ``test suite``: A series of tests of a certain function.
+2. ``test case``: A specific test instance in test suites.
+3. ``test service or partition``: Optional secure services or partitions to
+   support related test suites.
+
+Source structure
+================
+
++---------------------------------------+---------------------------------------------------------------+
+| Folder name                           | Description                                                   |
++=======================================+===============================================================+
+| test/bl1                              | TF-M bl1 test suites source code.                             |
++---------------------------------------+---------------------------------------------------------------+
+| test/bl2                              | TF-M bL2 test suites source code.                             |
++---------------------------------------+---------------------------------------------------------------+
+| test/config                           | The CMAKE test configurations files.                          |
++---------------------------------------+---------------------------------------------------------------+
+| test/framework                        | Source code for test framework code, managing test suites.    |
++---------------------------------------+---------------------------------------------------------------+
+| test/secure_fw/suites                 | Test suites divided into subdirectories.                      |
++---------------------------------------+---------------------------------------------------------------+
+| test/secure_fw/suites/<suite>/service | Test service divided into corresponding suite subdirectories. |
++---------------------------------------+---------------------------------------------------------------+
+| test/secure_fw/common_test_services   | Common test services.                                         |
++---------------------------------------+---------------------------------------------------------------+
+
+***********************
+Adding a new test suite
+***********************
+
+This section introduces how to add a new test suite and control its compilation
+with a test configuration in ``tf-m-tests`` repository.
+
+Source code
+===========
+
+The test suite example subdirectory named ``<test_name>`` is located under the
+path ``tf-m-tests/test/secure_fw/suites``. If the new test suite includes both
+non-secure and secure parts, the source code shall be divided shared code and
+specific code. An example test suite folder can be organized as the figure
+below.
+
+.. code-block:: bash
+
+    .
+    ├── CMakeLists.txt
+    ├── <test_name>_tests_common.c
+    ├── non_secure
+    │   ├── <test_name>_ns_interface_testsuite.c
+    │   └── <test_name>_ns_tests.h
+    └── secure
+        ├── <test_name>_s_interface_testsuite.c
+        └── <test_name>_s_tests.h
+
+Creating test configurations
+============================
+
+A test configuration controls whether one or multiple test suites are enabled.
+The doc `TF-M Build Instructionsn <https://tf-m-user-guide.trustedfirmware.org/technical_references/instructions/tfm_build_instruction.html>`_.
+shows some test configurations which are already supported in current TF-M.
+An example usage of test configuration shows below.
+
+.. code-block:: bash
+
+    cmake -S . -B cmake_build -DTFM_PLATFORM=arm/mps2/an521               \
+                              -DTFM_TOOLCHAIN_FILE=toolchain_GNUARM.cmake \
+                              -DCMAKE_BUILD_TYPE=Release                  \
+                              -DTEST_NS_ATTESTATION=ON
+
+With this command, only non-secure initial attestation test suite will be built.
+
+Developers shall assign corresponding test configurations to control the test
+suites.
+
+Naming test configurations
+--------------------------
+
+The test configurations of example test suites are ``TEST_NS_<TEST_NAME>``
+in non-secure and ``TEST_S_<TEST_NAME>`` in secure.
+
+.. Note::
+    The test configurations must be named with the prefixes ``TEST_S_`` and
+    ``TEST_NS_``, for secure regression tests and non-secure regression tests
+    respectively. Otherwise, tf-m-tests build system may not recognize it.
+
+Setting test configurations
+---------------------------
+
+When the test configurations have dependences, the default value need to be set.
+The setting is performed in following four steps.
+
+#. Command line input: The configuration can be enabled or disabled by the
+   command ``-DTEST_NS_<TEST_NAME>=ON/OFF -DTEST_S_<TEST_NAME>=ON/OFF``, and
+   the value cannot be changed throughout the whole compilation of TF-M tests.
+
+#. ``tf-m-tests/config/set_config.cmake``: The test configurations shall be
+   OFF if its dependences are not supported. The dependences are probably
+   from:
+
+    #. TF-M partitions configurations like ``TFM_PARTITION_CRYPTO``,
+       ``TFM_PARTITION_INITIAL_ATTESTATION``, etc.
+    #. TF-M build mode configuration like ``TFM_LIB_MODEL``.
+    #. TF-M other configurations like ``TFM_PARTITION_FIRMWARE_UPDATE``,
+       ``FORWARD_PROT_MSG``, etc.
+
+#. ``tf-m-tests/config/default_ns_test_config.cmake`` or
+   ``tf-m-tests/config/default_s_test_config.cmake``: It is required to give
+   the default value of the new test configuration in these two files when
+   ``TEST_NS`` or ``TEST_S`` is ON. The recommended value is ON unless the
+   single test's code or data size is very large.
+
+#. ``tf-m-tests/config/default_test_config.cmake``: It is required to give the
+   default value of the new test configuration in the file when both
+   ``TEST_NS`` and ``TEST_S`` are OFF. The default value must be OFF.
+
+.. Note::
+   The test configurations must be set as CACHE value in CMAKE files. The CACHE
+   set cannot replace the value from command line, see
+   `Set Cache Entry <https://cmake.org/cmake/help/latest/command/set.html#set-cache-entry>`_.
+
+Checking test configurations
+----------------------------
+
+The new test configurations must be checked by function ``tfm_invalid_config()``
+if they have any dependence. The value comes from command line may be wrong when
+the dependences are conflicting. In addition to the dependences quoted in
+``tf-m-tests/config/set_config.cmake``, some other test configurations may be
+necessary.
+
+Applicating test configurations
+===============================
+
+The mission of test configurations is to control the build. They are applied
+in ``test/secure_fw/suites/<test_name>/CMakeLists.txt`` like the example below.
+
+.. code-block:: cmake
+
+    cmake_policy(SET CMP0079 NEW)
+
+    if (NOT TEST_NS_<TEST_NAME> AND NOT TEST_S_<TEST_NAME>)
+        return()
+    endif()
+
+    ####################### Non Secure #########################################
+
+    if (TEST_NS_<TEST_NAME>)
+        add_library(tfm_test_suite_<test_name>_ns STATIC EXCLUDE_FROM_ALL)
+        # target_sources()
+        # target_include_directories()
+        target_compile_definitions(tfm_test_suite_<test_name>_ns
+            INTERFACE
+                TEST_NS_<TEST_NAME>
+        )
+        # target_link_libraries()
+    endif()
+
+    ####################### Secure #############################################
+
+    if (TEST_S_<TEST_NAME>)
+        add_library(tfm_test_suite_<test_name>_s STATIC EXCLUDE_FROM_ALL)
+        # target_sources()
+        # target_include_directories()
+        target_compile_definitions(tfm_test_suite_<test_name>_s
+            INTERFACE
+                TEST_S_<TEST_NAME>
+        )
+        # target_link_libraries()
+    endif()
+
+The function ``target_compile_definitions`` will export the macros
+``TEST_NS_<TEST_NAME>`` or ``TEST_S_<TEST_NAME>`` into source code. and in the
+file ``tf-m-tests/framework/non_secure_suites.c`` or
+``tests/framework/secure_suites.c``, the definitions of these macros will be
+checked, and then the head file will be included and test cases will be
+registered if the macro is defined.
+
+.. code-block:: c
+
+    #ifdef TEST_NS_<TEST_NAME>
+    #include "<test_name>_ns_tests.h"
+    #endif
+
+    static struct test_suite_t test_suites[] = {
+    /* Non-secure example test cases */
+        // ......
+    #ifdef TEST_NS_<TEST_NAME>
+        {&register_testsuite_ns_<test_name>_interface, 0, 0, 0},
+    #endif
+    };
+
+.. code-block:: c
+
+    #ifdef TEST_S_<TEST_NAME>
+    #include "<test_name>_s_tests.h"
+    #endif
+
+    static struct test_suite_t test_suites[] = {
+    /* Secure example test cases */
+        // ......
+    #ifdef TEST_S_<TEST_NAME>
+        {&register_testsuite_s_<test_name>_interface, 0, 0, 0},
+    #endif
+    };
+
+.. Note::
+    On most platforms non-secure tests and secure tests run on the same CPU
+    core, but dual-core platform is an exception. So secure test library and
+    secure sevices shall be linked together in the file
+    ``tf-m-tests/test/secure_fw/secure_tests.cmake``. Thus they can be built on
+    secure CPU core and non-secure tests library and RTOS are built on
+    non-secure CPU core.
+
+.. code-block:: cmake
+
+    if (TEST_FRAMEWORK_S)
+        # ...
+        if (TEST_S_<TEST_NAME>)
+            add_library(tfm_test_suite_<test_name>_s STATIC EXCLUDE_FROM_ALL)
+        endif()
+    endif()
+
+************************************
+Adding a new test case in test suite
+************************************
+
+The test cases usually express as a function in source code. They will be added
+into an array with structure type called ``test_t`` defined in
+``tf-m-tests/test/framework/test_framework.h``.
+
+.. code-block:: c
+
+    struct test_t {
+        TEST_FUN * const test;         /*!< Test function to call */
+        const char *name;              /*!< Test name */
+        const char *desc;              /*!< Test description */
+    };
+
+For example, a new test case called ``TFM_NS_<TEST_NAME>_TEST_1001`` is created
+and the function ``tfm_<test_name>_test_1001`` needs to be defined in file
+``<test_name>_ns_interface_testsuite.c``. Then the function shall be appended
+into the array which will be quoted in function
+``register_testsuite_ns_<test_name>_interface``. See the reference code below.
+
+.. code-block:: c
+
+    /* List of test cases */
+    static void tfm_<test_name>_test_1001(struct test_result_t *ret);
+
+    /* Append test cases */
+    static struct test_t <test_name>_tests[] = {
+        {&tfm_<test_name>_test_1001, "TFM_NS_<TEST_NAME>_TEST_1001",
+        "Example test case"},
+    };
+
+    /* Register test case into test suites */
+    void register_testsuite_ns_<test_name>_interface(struct test_suite_t *p_test_suite)
+    {
+        uint32_t list_size;
+
+        list_size = (sizeof(<test_name>_tests) / sizeof(<test_name>_tests[0]));
+
+        set_testsuite("<TEST_NAME> non-secure interface test (TFM_NS_<TEST_NAME>_TEST_1XXX)",
+                        <test_name>_tests, list_size, p_test_suite);
+    }
+
+    static void tfm_<test_name>_test_1001(struct test_result_t *ret)
+    {
+       /* test case code */
+    }
+
+********************
+Adding test services
+********************
+
+Some test group may need specific test services. These test services may support
+one or more groups thus developers shall determine the proper test scope. Refer
+to
+`Adding partitions for regression tests <https://git.trustedfirmware.org/TF-M/tf-m-tests.git/tree/docs/tfm_test_services_addition.rst>`_
+to get more information.
+
+**********************************
+Out-of-tree regression test suites
+**********************************
+
+TF-M supports out-of-tree regression test suites build, whose source code
+folders are maintained outside tf-m-tests repo. There are two configurations
+for developers to include the source code.
+
+- ``EXTRA_NS_TEST_SUITES_PATHS``
+
+  A list of the absolute directories of the out-of-tree non-secure test suites
+  source code folder(s). TF-M build system searches ``CMakeLists.txt`` of
+  non-secure test suites in the source code folder(s).
+  Use semicolons ``;`` to separate multiple out-of-tree non-secure test suites
+  directorires.
+
+- ``EXTRA_S_TEST_SUITES_PATHS``
+
+  A list of the absolute directories of the out-of-tree secure test suites
+  source code folder(s).
+
+Example usage
+=============
+
+Take non-secure test as an example in
+`tf-m-extras <https://git.trustedfirmware.org/TF-M/tf-m-extras.git/>`_.
+A single out-of-tree test suite folder can be organized as the figure below:
+
+.. code-block:: bash
+
+    extra_ns
+    ├── CMakeLists.txt
+    ├── ns_test.c
+    ├── ns_test_config.cmake
+    └── ns_test.h
+
+In the example above, ``EXTRA_NS_TEST_SUITES_PATHS`` in the build command can be
+specified as listed below.
+
+.. code-block:: bash
+
+  -DEXTRA_NS_TEST_SUITES_PATHS=<Absolute-path-extra-test-folder>
+
+Coding instructions
+===================
+
+This is a demo of source code so the structure has been simplified. Files like
+``ns_test.c`` and ``ns_test.h`` can be expanded to ``src`` and ``include``
+folders. The ``CMakeLists.txt`` is required in the root path and
+``ns_test_config.cmake`` is optional.
+
+Header Files
+------------
+
+The header file ``extra_ns_tests.h`` must be included by out-of-tree source
+code. This file contains the definition of ``struct extra_tests_t``,
+``int32_t register_extra_tests()`` and declaration of
+``int32_t extra_ns_tests_init()``.
+
+Source code
+-----------
+
+To connect the out-of-tree source code and tf-m-tests framework, the high-level
+test function must be defined first. An example format is:
+
+.. code-block:: c
+
+    int32_t ns_test(void)
+    {
+        /* Add platform specific non-secure test suites code here. */
+
+        return EXTRA_TEST_SUCCESS;
+    }
+
+This function is the main entry to test framework. All the out-of-tree's test
+cases can be added into it. The returned error code of this function is
+specified as ``int32_t``. This function shall return an expected value which is
+same as the part ``expected_ret`` set in ``plat_ns_t`` below, take the macro
+EXTRA_TEST_SUCCESS as an example.
+
+After ``ns_test()`` is defined, a structure variable need to be created like:
+
+.. code-block:: c
+
+    const struct extra_tests_t plat_ns_t = {
+        .test_entry = ns_test,
+        .expected_ret = EXTRA_TEST_SUCCESS
+    };
+
+It will be used by function ``extra_ns_tests_init()`` to register the test by
+function ``register_extra_tests()``:
+
+.. code-block:: c
+
+    int32_t extra_ns_tests_init(struct extra_tests_t *internal_test_t)
+    {
+        /* Add platform init code here. */
+
+        return register_extra_tests(internal_test_t, &plat_ns_t);
+    }
+
+The platform initialization code can be added in this function because it runs
+before ``ns_test()``.
+
+.. Note::
+    Function ``extra_ns_tests_init()`` is declared in tf-m-tests repository
+    without definition. It is supplied to out-of-tree source code and need to be
+    defined with no change of its format, like returns error code and parameter
+    name.
+
+
+CMakeLists.txt
+--------------
+
+In addition to the implementation of CMAKE target like ``example_test_ns`` of
+out-of-tree source code, the configuration below needs to be appended:
+
+.. code-block:: cmake
+
+    # Example test must link tfm_test_suite_extra_common to use related interface
+    target_link_libraries(example_test_ns
+        PRIVATE
+            tfm_test_suite_extra_common
+    )
+
+    # The example_test_ns library must be linked by tfm_test_suite_extra_common
+    target_link_libraries(tfm_test_suite_extra_ns
+        PRIVATE
+            example_test_ns
+    )
+
+To use the interfaces come from tf-m-tests repository, library
+``tfm_test_suite_extra_common`` must be linked by ``example_test_ns``.
+To add out-of-tree test into TF-M, library ``example_test_ns`` must be linked
+by ``tfm_test_suite_extra_ns``.
+
+ns_test_config.cmake
+--------------------
+
+The CMAKE configuration file is optional. If out-of-tree source already exists
+another configuration file, a new one can be ignored.
+
+--------------
+
+*Copyright (c) 2021-2022, Arm Limited. All rights reserved.*
diff --git a/readme.rst b/readme.rst
index 4b6cefe..5f885e0 100644
--- a/readme.rst
+++ b/readme.rst
@@ -16,6 +16,7 @@
 
 - app - The application code that executes the testing, including both the TF-M
   tests and the `psa-arch-tests`_.
+- docs - The documents about test developments.
 - CMSIS - The libraries of RTX which is the Non-secure RTOS of the tests
 - test - The TF-M test codes including test framework, test suites and test
   services
@@ -30,4 +31,4 @@
 .. _Trusted Firmware-M: https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/
 .. _psa-arch-tests: https://github.com/ARM-software/psa-arch-tests
 
-*Copyright (c) 2020, Arm Limited. All rights reserved.*
+*Copyright (c) 2020-2022, Arm Limited. All rights reserved.*