diff --git a/docs/configuration/kconfig_system.rst b/docs/configuration/kconfig_system.rst
index 41a3d4f..f4fa257 100644
--- a/docs/configuration/kconfig_system.rst
+++ b/docs/configuration/kconfig_system.rst
@@ -27,16 +27,20 @@
 
   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`_.
 
-- The .config file
+- The .config and .config.old files
 
   The ``.config`` file which contains all the above configurations in the Kconfig format.
-  It is only used to allow users to make adjustments basing on the previous settings.
-  The Kconfig tool will load it if it exists.
+  It will be created after the first execution of the script. It is only used to allow
+  users to make adjustments basing on the previous settings.
+  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 three arguments at maximum.
+The script takes four arguments at maximum.
 
 - '-k', '--kconfig-file'
 
@@ -53,13 +57,34 @@
 
   Required. The output directory to hold the generated files.
 
-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
+- '-p', '--platform-path'
+
+  Optional. The platform specific Kconfig or defconfig files.
+
+Here is an example:
+
+.. 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`` and CMake will launch the GUI menuconfig
-for users to adjust configurations and automatically load the generated config files.
+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.
 
 .. note::
 
@@ -70,14 +95,11 @@
 *****************
 The Kconfig files
 *****************
-The Kconfig files are the files written in the
+The Kconfig files are the files written by the
 `Kconfig language <https://www.kernel.org/doc/html/latest/kbuild/kconfig-language.html#kconfig-language>`__
 to describe config options.
-They also uses some Kconfiglib extensions such as ``osource`` and ``rsource`` so they can only work
-with the Kconfiglib.
-
-Component options are gathered together in a seperate menu ``TF-M component configs`` because these
-options are changed less frequently.
+They also uses some Kconfiglib extensions such as optional source ``osource`` and relative source ``rsource``
+so they can only work with the Kconfiglib.
 
 --------------