binman: Automatically include a U-Boot .dtsi file

For boards that need U-Boot-specific additions to the device tree, it is
a minor annoyance to have to add these each time the tree is synced with
upstream.

Add a means to include a file (e.g. u-boot.dtsi) automatically into the .dts
file before it is compiled.

The file uses is the first one that exists in this list:

   arch/<arch>/dts/<board.dts>-u-boot.dtsi
   arch/<arch>/dts/<soc>-u-boot.dtsi
   arch/<arch>/dts/<cpu>-u-boot.dtsi
   arch/<arch>/dts/<vendor>-u-boot.dtsi
   arch/<arch>/dts/u-boot.dtsi

Signed-off-by: Simon Glass <sjg@chromium.org>
Suggested-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/tools/binman/README b/tools/binman/README
index 45e741e..cb47e73 100644
--- a/tools/binman/README
+++ b/tools/binman/README
@@ -422,6 +422,45 @@
 step.
 
 
+Automatic .dtsi inclusion
+-------------------------
+
+It is sometimes inconvenient to add a 'binman' node to the .dts file for each
+board. This can be done by using #include to bring in a common file. Another
+approach supported by the U-Boot build system is to automatically include
+a common header. You can then put the binman node (and anything else that is
+specific to U-Boot, such as u-boot,dm-pre-reloc properies) in that header
+file.
+
+Binman will search for the following files in arch/<arch>/dts:
+
+   <dts>-u-boot.dtsi where <dts> is the base name of the .dts file
+   <CONFIG_SYS_SOC>-u-boot.dtsi
+   <CONFIG_SYS_CPU>-u-boot.dtsi
+   <CONFIG_SYS_VENDOR>-u-boot.dtsi
+   u-boot.dtsi
+
+U-Boot will only use the first one that it finds. If you need to include a
+more general file you can do that from the more specific file using #include.
+If you are having trouble figuring out what is going on, you can uncomment
+the 'warning' line in scripts/Makefile.lib to see what it has found:
+
+   # Uncomment for debugging
+   # $(warning binman_dtsi_options: $(binman_dtsi_options))
+
+
+Code coverage
+-------------
+
+Binman is a critical tool and is designed to be very testable. Entry
+implementations target 100% test coverage. Run 'binman -T' to check this.
+
+To enable Python test coverage on Debian-type distributions (e.g. Ubuntu):
+
+   $ sudo apt-get install python-pip python-pytest
+   $ sudo pip install coverage
+
+
 Advanced Features / Technical docs
 ----------------------------------