doc: Add documentation for how to build U-Boot host tools
This adds a reST document for how to build U-Boot host tools,
including information for both Linux and Windows.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/doc/build/tools.rst b/doc/build/tools.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+.. sectionauthor:: Bin Meng <bmeng.cn@gmail.com>
+
+Host tools
+==========
+
+Building tools for Linux
+------------------------
+
+To allow distributions to distribute all possible tools in a generic way,
+avoiding the need of specific tools building for each machine, a tools only
+defconfig file is provided.
+
+Using this, we can build the tools by doing::
+
+ $ make tools-only_defconfig
+ $ make tools-only
+
+Building tools for Windows
+--------------------------
+If you wish to generate Windows versions of the utilities in the tools directory
+you can use MSYS2, a software distro and building platform for Windows.
+
+Download the MSYS2 installer from https://www.msys2.org. Make sure you have
+installed all required packages below in order to build these host tools::
+
+ * gcc (9.1.0)
+ * make (4.2.1)
+ * bison (3.4.2)
+ * diffutils (3.7)
+ * openssl-devel (1.1.1.d)
+
+Note the version numbers in these parentheses above are the package versions
+at the time being when writing this document. The MSYS2 installer tested is
+http://repo.msys2.org/distrib/x86_64/msys2-x86_64-20190524.exe.
+
+There are 3 MSYS subsystems installed: MSYS2, MinGW32 and MinGW64. Each
+subsystem provides an environment to build Windows applications. The MSYS2
+environment is for building POSIX compliant software on Windows using an
+emulation layer. The MinGW32/64 subsystems are for building native Windows
+applications using a linux toolchain (gcc, bash, etc), targeting respectively
+32 and 64 bit Windows.
+
+Launch the MSYS2 shell of the MSYS2 environment, and do the following::
+
+ $ make tools-only_defconfig
+ $ make tools-only NO_SDL=1