doc/soc/intel/xeon_sp: Add Xeon-SP coreboot community preview guide

The community preview branch for coreboot on latest Xeon Scalable
processor is opensource at:
https://review.coreboot.org/plugins/gitiles/intel-dev-pub/.

Change-Id: Ie2ffc1722a4a26d6039b6642efa95bf072d896ad
Signed-off-by: Shuo Liu <shuo.liu@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78787
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>

Documentation/soc/intel/index.md

@@ -12,3 +12,4 @@ This section contains documentation about coreboot on specific Intel SOCs.
 - [Firmware Interface Table](fit.md)
 - [Apollolake](apollolake/index.md)
 - [CSE FW Update](cse_fw_update/cse_fw_update.md)
+- [Xeon Scalable processor](xeon_sp/index.md)

Documentation/soc/intel/xeon_sp/community_preview_guide.md

@@ -0,0 +1,120 @@
+Xeon Scalable processor coreboot Community Preview Guide
+================================================
+
+## Background
+
+Sapphire Rapids coreboot was already merged into coreboot mainline.
+Granite Rapids coreboot upstreaming is coming.
+
+For Granite Rapids coreboot, we are going to perform a phased
+upstreaming strategy according to the maturity of the code. A community
+preview branch is opensource at:
+https://review.coreboot.org/plugins/gitiles/intel-dev-pub/.
+
+The community preview branch initially contains codes on legacy feature
+enabling and matured patch set for platform support. More platform
+support code will come with the platform development. The subsequent
+upstreaming work will be based on this branch. It provides 2 board
+targets,
+
+1. Avenue City CRB (Granite Rapids-AP)
+2. Beechnut City CRB (Granite Rapids-SP)
+
+The above targets can pass build with Granite Rapids n-1 FSP headers,
+which is a set of stub FSP headers used for compilation sanity check.
+
+## Build steps
+
+### Prepare workspace
+
+```
+# Create workspace
+
+mkdir workspace && cd workspace
+
+# Prepare coreboot codebase
+
+git clone https://review.coreboot.org/intel-dev-pub ln -s intel-dev-pub/
+coreboot
+
+# Prepare stub binaries and update their path in
+# configs/builder/config.intel.crb.avc.n-1
+
+# Granite Rapids coreboot uses FSP 2.4, where FSP-I is newly introduced
+# as an optional module to provide FSP based SMM capability. For FSP 2.4
+# and FSP-I, please further refer to:
+# https://cdrdv2-public.intel.com/736809/736809_FSP_EAS_v2.4_Errata_A.pdf
+
+CONFIG_IFD_BIN_PATH=<path of intel flash descriptor blob>
+CONFIG_CPU_UCODE_BINARIES=<path of ucode>
+CONFIG_FSP_T_FILE=<path of FSP-T binary>
+CONFIG_FSP_M_FILE=<path of FSP-M binary>
+CONFIG_FSP_S_FILE=<path of FSP-S binary>
+CONFIG_FSP_I_FILE=<path of FSP-I binary>
+CONFIG_PAYLOAD_FILE=<path of payload binary>
+```
+
+### Download necessary submodules
+```
+git submodule update --init --checkout 3rdparty/vboot
+```
+
+### Or take below alternative if the network connection is not good
+```
+git clone https://github.com/coreboot/vboot.git 3rdparty/vboot/
+```
+
+### Build toolchain
+```
+make crossgcc-i386 CPUS=$(nproc)
+```
+
+### Build BIOS (Avenue City CRB)
+```
+make distclean
+
+make defconfig KBUILD_DEFCONFIG=configs/builder/config.intel.crb.avc.n-1
+
+make olddefconfig
+
+make clean
+
+make UPDATED_SUBMODULES=1 -j`nproc`
+```
+
+### Build BIOS (Beechnut City CRB)
+```
+make distclean
+
+make defconfig KBUILD_DEFCONFIG=configs/builder/config.intel.crb.bnc.n-1
+
+make olddefconfig
+
+make clean
+
+make UPDATED_SUBMODULES=1 -j`nproc`
+```
+
+### Obtain the preview patch list
+
+```
+# The tag ‘upstream’ points to the upstream commit that the preview
+# branch is based on.
+
+git format-patch upstream..HEAD
+```
+
+## About Granite Rapids n-1 FSP Headers
+
+This is a set of stub FSP headers for Granite Rapids server, which will
+be forward compatible with the formal Granite Rapids FSP headers which
+will be opensource at a later stage. For the n-1 FSP headers, there are
+no corresponding n-1 FSP binaries. To pass build, users need to use stub
+binaries which could be generated in arbitrary ways.  Granite Rapids n-1
+FSP headers are at: `src/vendorcode/intel/fsp/fsp2_0/graniterapids_n-1`.
+
+For the formal Granite Rapids FSP headers and binaries, they will be
+published at in
+https://github.com/coreboot/coreboot/tree/main/src/vendorcode/intel/fsp/fsp2_0
+(headers only) and https://github.com/intel/FSP (headers and binaries)
+at a later stage.

Documentation/soc/intel/xeon_sp/index.md

@@ -0,0 +1,8 @@
+# Xeon Scalable processor documentation
+
+This section contains documentation about coreboot on Xeon Scalable
+processors.
+
+## Topics
+
+- [Community preview guide](community_preview_guide.md)