Platform: Adding Nuvoton M2351 Support

The NuMicro® M2351 microcontroller series is powered by Arm® Cortex®-M23
core with TrustZone® for Armv8-M architecture, which elevates the
traditional firmware security to the new level of robust software
security.

The porting will apply trusted-firmware-M to M2351 to make it easy to
create the security firmware on Nuvoton M2351 platform.

Signed-off-by: WSChang <wschang0@nuvoton.com>

Change-Id: I059618223fae8ab9ca085e9c998d51e3d12e8d86
diff --git a/docs/introduction/readme.rst b/docs/introduction/readme.rst
index e8fb4e7..ef6f06b 100644
--- a/docs/introduction/readme.rst
+++ b/docs/introduction/readme.rst
@@ -150,6 +150,8 @@
 
         - `FPGA image loaded on MPS2 board (AN519, AN539).
           <https://developer.arm.com/products/system-design/development-boards/cortex-m-prototyping-systems/mps2>`_
+        - `M2351.
+          <https://www.nuvoton.com/products/iot-solution/iot-platform/numaker-pfm-m2351/>`_
 
     - Dual Core Cortex-M system: