Platform: Add full support for PSoC64 platform

Add support for the Cypress CYS0644ABZI-S2D44 board.

This support was developed over the course of 2019 in
the feature-twincpu branch. Full commit history is
available there.

Signed-off-by: Chris Brand <chris.brand@cypress.com>
Change-Id: I709633d04227b71aea87aee84fd63a48c7d26fb1
diff --git a/docs/user_guides/tfm_build_instruction.rst b/docs/user_guides/tfm_build_instruction.rst
index db6e0fe..16d8945 100644
--- a/docs/user_guides/tfm_build_instruction.rst
+++ b/docs/user_guides/tfm_build_instruction.rst
@@ -212,6 +212,9 @@
             ``-DTARGET_PLATFORM=MUSCA_S1``
           - Cortex-M33 SSE-200 subsystem for MPS3 (AN524)
             ``-DTARGET_PLATFORM=AN524``
+          - Cypress CYS0644ABZI-S2D44 board (PSoC64 platform)
+            ``-DTARGET_PLATFORM=psoc64``
+            See :doc:`Cypress PSoC 64 platform specifics </platform/ext/target/cypress/psoc64/cypress_psoc_64_spec>`
 
    * - -DCOMPILER=<compiler name>
      - Specifies the compiler toolchain