docs: Add platform support guide

This patch adds initial platform support guide (i.e.
docs/platform_guide.md).

Signed-off-by: Anup Patel <anup.patel@wdc.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/docs/platform_guide.md b/docs/platform_guide.md
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+OpenSBI Platform Support Guideline
+==================================
+
+The OpenSBI platform support is a set of platform specific hooks provided
+in the form of a *struct sbi_platform* instance. It is required by:
+
+1. *libplatsbi.a* - A platform specific OpenSBI static library, that is,
+   libsbi.a plus a *struct sbi_platform* instance installed at
+   *<install_directory>/platform/<platform_subdir>/lib/libplatsbi.a*
+2. *firmwares* - Platform specific bootable firmware binaries installed at
+   *<install_directory>/platform/<platform_subdir>/bin*
+
+A complete doxygen-style documentation of *struct sbi_platform* and related
+APIs is available in sbi/sbi_platform.h.
+
+Adding a new platform support
+-----------------------------
+
+The support of a new platform named *<xyz>* can be added as follows:
+
+1. Create a directory named *<xyz>* under *platform/* directory
+2. Create a platform configuration file named *config.mk* under
+   *platform/<xyz>/* directory. This configuration file will provide
+   compiler flags, select common drivers, and select firmware options
+3. Create *platform/<xyz>/objects.mk* file for listing the platform
+   specific object files to be compiled
+4. Create *platform/<xyz>/platform.c* file providing a *struct sbi_platform*
+   instance
+
+A template platform support code is available under the *platform/template*.
+Copying this directory as new directory named *<xyz>* under *platform/*
+directory will create all the files mentioned above.