doc: SPL: Add README for secure boot support

Adds information regarding SPL handling validation process of main u-boot
image on power/mpc85xx and arm/layerscape platforms.

Signed-off-by: Sumit Garg <sumit.garg@nxp.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: York Sun <york.sun@nxp.com>
This commit is contained in:
Sumit Garg 2016-07-14 12:27:53 -04:00 committed by York Sun
parent aa36c84edf
commit ebfc066e6f

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Overview of SPL verified boot on powerpc/mpc85xx & arm/layerscape platforms
===========================================================================
Introduction
------------
This document provides an overview of how SPL verified boot works on powerpc/
mpc85xx & arm/layerscape platforms.
Methodology
-----------
The SPL image is responsible for loading the next stage boot loader, which is
the main u-boot image. For secure boot process on these platforms ROM verifies
SPL image, so to continue chain of trust SPL image verifies U-boot image using
spl_validate_uboot(). This function uses QorIQ Trust Architecture header
(appended to U-boot image) to validate the U-boot binary just before passing
control to it.