[edk2-platforms][PATCH V6 16/16] Platform/Loongson: Add Readme.

["xianglai" <lixianglai@loongson.cn>]

Add Readme for LoogArch and Modify the Readme in the root directory.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4054

Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Bibo Mao <maobibo@loongson.cn>
Cc: Chao Li <lichao@loongson.cn>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Signed-off-by: xianglai li <lixianglai@loongson.cn>
Reviewed-by: Chao Li <lichao@loongson.cn>
---
 Platform/Loongson/LoongArchQemuPkg/Readme.md | 60 ++++++++++++++++++++
 Readme.md                                    |  9 +++
 2 files changed, 69 insertions(+)
 create mode 100644 Platform/Loongson/LoongArchQemuPkg/Readme.md

diff --git a/Platform/Loongson/LoongArchQemuPkg/Readme.md b/Platform/Loongson/LoongArchQemuPkg/Readme.md
new file mode 100644
index 0000000000..7b11905f14
--- /dev/null
+++ b/Platform/Loongson/LoongArchQemuPkg/Readme.md
@@ -0,0 +1,60 @@
+# Introduction
+
+  This document provides the guideline to build UEFI firmware for Qemu of LoongArch.
+
+  LoongArch is the general processor architecture of Loongson.
+
+  We can get the latest LoongArch documents or LoongArch tools at https://github.com/loongson/.
+
+# How to build (X86 Linux Environment)
+
+  1. Install LoongArch cross-tools on X86 machines.
+    Download cross-tools from https://github.com/loongson/build-tools ,Then config cross-tools env.
+    For Example:
+
+    $ wget https://github.com/loongson/build-tools/releases/download/2022.09.06/loongarch64-clfs-6.3-cross-tools-gcc-glibc.tar.xz
+    $ tar -vxf loongarch64-clfs-6.3-cross-tools-gcc-glibc.tar.xz  -C /opt
+    $ export PATH=/opt/cross-tools/bin:$PATH
+
+    Note: Please obtain the latest cross-compilation tools from https://github.com/loongson/build-tools .
+
+  2. Follow edk2-platforms/Readme.md to obtaining source code,And config build env.
+    For Example:
+
+    $ export WORKSPACE=/work/git/tianocore
+    $ mkdir -p $WORKSPACE
+    $ cd $WORKSPACE
+    $ git clone https://github.com/tianocore/edk2.git
+    $ git submodule update --init
+    $ git clone https://github.com/tianocore/edk2-platforms.git
+    $ git submodule update --init
+    $ git clone https://github.com/tianocore/edk2-non-osi.git
+    $ export PACKAGES_PATH=$PWD/edk2:$PWD/edk2-platforms:$PWD/edk2-non-osi
+
+  3. Config  cross compiler prefix.
+    For Example:
+
+    $ export GCC5_LOONGARCH64_PREFIX=loongarch64-unknown-linux-gnu-
+
+  4.Set up the build environment And  build BaseTool.
+    For Example:
+
+    $. edk2/edksetup.sh
+    $make -C edk2/BaseTools
+
+  5.Build  platform.
+    For Exmaple:
+
+    $build --buildtarget=DEBUG --tagname=GCC5 --arch=LOONGARCH64  --platform=Platform/Loongson/LoongArchQemuPkg/Loongson.dsc
+
+  After a successful build, the resulting images can be found in `Build/{Platform Name}/{TARGET}_{TOOL_CHAIN_TAG}/FV/QEMU_EFI.fd`.
+
+  A compile script is provided here:
+
+    #!/bin/bash
+    export WORKSPACE=/work/git/tianocore
+    export PACKAGES_PATH=$WORKSPACE/edk2:$WORKSPACE/edk2-platforms
+    export GCC5_LOONGARCH64_PREFIX=loongarch64-unknown-linux-gnu-
+    . edk2/edksetup.sh
+    make -C edk2/BaseTools
+    build --buildtarget=DEBUG --tagname=GCC5 --arch=LOONGARCH64  --platform=Platform/Loongson/LoongArchQemuPkg/Loongson.dsc
diff --git a/Readme.md b/Readme.md
index 62876b4b7d..93e4dc5255 100644
--- a/Readme.md
+++ b/Readme.md
@@ -57,6 +57,7 @@ IA32                | i?86-linux-gnu-* _or_ x86_64-linux-gnu-
 IPF                 | ia64-linux-gnu
 X64                 | x86_64-linux-gnu-
 RISCV64             | riscv64-unknown-elf-
+LOONGARCH64         | loongarch64-unknown-linux-
 
 \* i386, i486, i586 or i686
 
@@ -71,6 +72,11 @@ RISC-V open source community provides GCC toolchains for
 [riscv64-unknown-elf](https://github.com/riscv/riscv-gnu-toolchain)
 compiled to run on x86 Linux.
 
+### GCC for LoongArch
+Loonson open source community provides GCC toolchains for
+[loongarch64-unknown-elf](https://github.com/loongson/build-tools)
+compiled to run on x86 Linux
+
 ### clang
 Clang does not require separate cross compilers, but it does need a
 target-specific binutils. These are included with any prepackaged GCC toolchain
@@ -257,6 +263,9 @@ For more information, see the
 ##### Minnowboard Max/Turbot based on Intel Valleyview2 SoC
 * [Minnowboard Max](Platform/Intel/Vlv2TbltDevicePkg)
 
+## Loongson
+* [LoongArchQemu](Platform/Loongson/LoongArchQemuPkg)
+
 ## Marvell
 * [Armada 70x0](Platform/Marvell/Armada70x0Db)
 * [Armada 80x0](Platform/Marvell/Armada80x0Db)
-- 
2.31.1