Platform: Add FVP_SSE300_MPS2 target

Add support for FVP_SSE300_MPS2 platform

Change-Id: Ieddb5adbdc0cc47690bbe0b3dfbaf39d005d03ea
Signed-off-by: Mark Horvath <mark.horvath@arm.com>
Signed-off-by: Marton Berke <marton.berke@arm.com>
diff --git a/docs/user_guides/tfm_build_instruction.rst b/docs/user_guides/tfm_build_instruction.rst
index d19077f..8ed8c2d 100644
--- a/docs/user_guides/tfm_build_instruction.rst
+++ b/docs/user_guides/tfm_build_instruction.rst
@@ -250,6 +250,8 @@
             ``-DTARGET_PLATFORM=AN519``
           - Arm SSE-123 Example Subsystem for MPS2+ (AN539)
             ``-DTARGET_PLATFORM=AN539``
+          - Cortex-M55 SSE-300 subsystem for MPS2+ FVP
+            ``-DTARGET_PLATFORM=FVP_SSE300_MPS2``
           - Musca-A test chip board (Cortex-M33 SSE-200 subsystem)
             ``-DTARGET_PLATFORM=MUSCA_A``
           - Musca-B1 test chip board (Cortex-M33 SSE-200 subsystem)