diff --git a/docs/configuration/kconfig_system.rst b/docs/configuration/kconfig_system.rst
index f4fa257..a4b2caf 100644
--- a/docs/configuration/kconfig_system.rst
+++ b/docs/configuration/kconfig_system.rst
@@ -3,30 +3,32 @@
 ##################
 The Kconfig System
 ##################
-The Kconfig system is an additional tool for users to change configuration options of TF-M.
+The Kconfig system is an alternative tool to the CMake config system for users to change config
+options of TF-M.
 
 .. figure:: kconfig_header_file_system.png
 
 It handles dependencies and validations automatically when you change configurations so that the
 generated configuration options are always valid.
 
-It consists of `The Kconfig tool`_ and the `The Kconfig files`_.
+To use the Kconfig system, enable ``USE_KCONFIG_TOOL`` in commande line.
+And enable ``MENUCONFIG`` to launch configuration GUI.
+
+The Kconfig system consists of `The Kconfig tool`_ and the `The Kconfig files`_.
 
 ****************
 The Kconfig tool
 ****************
 The Kconfig tool is a python script based on `Kconfiglib <https://github.com/ulfalizer/Kconfiglib>`__
-to launch the menuconfig interfaces and generate the following config files:
+to generate the following config files:
 
 - CMake config file
 
   Contains CMake cache variables of building options.
-  This file should be passed to the build system via command line option ``TFM_EXTRA_CONFIG_PATH``.
 
 - Header file
 
   Contains component options in the header file system.
-  This file should be passed to the build system via the command line option ``PROJECT_CONFIG_HEADER_FILE``.
   Component options are gathered together in a seperate menu ``TF-M component configs`` in
   `The Kconfig files`_.
 
@@ -38,59 +40,74 @@
   The Kconfig tool will load it if it exists and ``.config.old`` will be created to
   save the previous configurations.
 
-How To Use
-==========
-The script takes four arguments at maximum.
+The tool supports loading multiple pre-set configuration files merging into a single one.
+The first loaded options are overridden by later ones if the config files contain duplicated
+options.
+And dependencies between config options are taken care of.
+It then launchs a configuration GUI for users to change any config options if the ``MENUCONFIG`` is
+enabled in build command line.
 
-- '-k', '--kconfig-file'
+Integration with TF-M build system
+----------------------------------
+TF-M build system includes ``kconfig.cmake`` to integrate this tool.
+It prepares the parameters for the script and invokes it to load multiple configuration files basing
+on your build setup, including but not limited to
 
-  Required. The root Kconfig file.
+  - Build type bound configurations, decided by ``CMAKE_BUILD_TYPE``
+  - Profile configurations, decided by ``TFM_PROFILE``
 
-- '-u', '--ui'
+**************************
+Customizing config options
+**************************
+By default, the Kconfig system only merges configuration files and generated the final config files.
+To customize the config options, there are several approaches.
 
-  Optional. The menuconfig interface to launch, ``gui`` or ``tui``.
-  Refer to `Menuconfig interfaces <https://github.com/ulfalizer/Kconfiglib#menuconfig-interfaces>`__
-  for interface details. Only the first two are supported.
-  If no UI is selected, the tool generates config files with default values.
+Menuconfig
+----------
+Menuconfig is the recommended approach to adjust the values of the config options because it has
+a graphic interface for you to easily change the options without worrying about dependencies.
 
-- '-o', '--output_path'
-
-  Required. The output directory to hold the generated files.
-
-- '-p', '--platform-path'
-
-  Optional. The platform specific Kconfig or defconfig files.
-
-Here is an example:
+To launch the menuconfig, you need to enable ``MENUCONFIG`` in addition to enabling
+``USE_KCONFIG_TOOL``.
 
 .. code-block:: bash
 
-  cd trusted-firmware-m
-  python3 tools/kconfig/tfm_kconfig.py -k Kconfig -o <output_path> -u tui
-
-  # If the platform path has defconfig or Kconfig, use '-p' to load them.
-  python3 tools/kconfig/tfm_kconfig.py -k Kconfig -o <output_path> -p platform/ext/target/arm/mps2/an521
-
-The script can be used as a standalone tool. You can pass the config files to
-build system via command line option ``TFM_EXTRA_CONFIG_PATH`` and
-``PROJECT_CONFIG_HEADER_FILE`` respectively, as mentioned above.
-
-.. code-block:: bash
-
-  # Pass the files generated by script.
-  <cmake build command> -DTFM_EXTRA_CONFIG_PATH=<output_path>/project_config.cmake \
-                        -DPROJECT_CONFIG_HEADER_FILE=<output_path>/project_config.h
-
-The TF-M build system has also integrated the tool.
-You only need to set ``USE_KCONFIG_TOOL`` to ``ON/TRUE/1`` in commande line and CMake will launch
-the GUI menuconfig for users to adjust configurations and automatically load the generated config
-files.
+  cmake -S . -B cmake_build -DTFM_PLATFORM=arm/mps2/an521 \
+                            -DUSE_KCONFIG_TOOL=ON \
+                            -DMENUCONFIG=ON
 
 .. note::
 
-  - Only GUI menuconfig can be launched by CMake for the time being.
-  - Due to the current limitation of the tool, you are not allowed to change the values of build
-    options that of which platforms have customized values. And there is no prompt messages either.
+  Although the Kconfiglib provides three
+  `menuconfig interfaces <https://github.com/ulfalizer/Kconfiglib#menuconfig-interfaces>`__,
+  only GUI menuconfig can be launched by CMake for the time being.
+
+Command line options
+--------------------
+The support of passing configurations via command line is kept for the Kconfig system.
+
+.. code-block:: bash
+
+  cmake -S . -B cmake_build -DTFM_PLATFORM=arm/mps2/an521 \
+                            -DUSE_KCONFIG_TOOL=ON \
+                            -DTFM_ISOLATION_LEVEL=2
+
+Kconfig file
+------------
+You can also put the frequently used config options into a Kconfig file. When you need to apply the
+config options in that file, pass it via command line option ``-DKCONFIG_CONFIG_FILE``
+
+.. code-block:: bash
+
+  cmake -S . -B cmake_build -DTFM_PLATFORM=arm/mps2/an521 \
+                            -DTFM_ISOLATION_LEVEL=2 \
+                            -DUSE_KCONFIG_TOOL=ON \
+                            -DKCONFIG_CONFIG_FILE=my_config.conf
+
+.. note::
+
+  The command line set options override the ones in the config file.
+  And you can always launch menuconfig to do the final adjustments.
 
 *****************
 The Kconfig files
@@ -103,4 +120,4 @@
 
 --------------
 
-*Copyright (c) 2022, Arm Limited. All rights reserved.*
+*Copyright (c) 2022-2023, Arm Limited. All rights reserved.*