doc: Move content from Porting Guide
The Porting Guide document is broken down into separate,
per-topic documents that all live under the new "Porting"
chapter.
Change-Id: I269fa06cbf6544ce3c76700d1fcf3a669793c483
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
Signed-off-by: Jimmy Brisson <jimmy.brisson@arm.com>
diff --git a/docs/porting/optional-mods.rst b/docs/porting/optional-mods.rst
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+Optional modifications
+======================
+
+The following are helper functions implemented by the test framework that
+perform common platform-specific tasks. A platform may choose to override these
+definitions.
+
+Function : platform_get_stack()
+```````````````````````````````
+
+::
+
+ Argument : unsigned long
+ Return : unsigned long
+
+This function returns the base address of the memory stack that has been
+allocated for the CPU specified by MPIDR. The size of the stack allocated to
+each CPU is specified by the platform defined constant ``PLATFORM_STACK_SIZE``.
+
+Common implementation of this function is provided in
+``plat/common/aarch64/platform_mp_stack.S``.
+
+Function : tftf_platform_end()
+``````````````````````````````
+
+::
+
+ Argument : void
+ Return : void
+
+This function performs any operation required by the platform to properly finish
+the test session.
+
+The default implementation sends an EOT (End Of Transmission) character on the
+UART. This can be used to automatically shutdown the FVP models. When running on
+real hardware, the UART output may be parsed by an external tool looking for
+this character and rebooting the platform for example.
+
+Function : tftf_plat_reset()
+````````````````````````````
+
+::
+
+ Argument : void
+ Return : void
+
+This function resets the platform.
+
+The default implementation uses the ARM watchdog peripheral (`SP805`_) to
+generate a watchdog timeout interrupt. This interrupt remains deliberately
+unserviced, which eventually asserts the reset signal.
+
+--------------
+
+*Copyright (c) 2019, Arm Limited. All rights reserved.*
+
+.. _SP805: https://static.docs.arm.com/ddi0270/b/DDI0270.pdf