boards: amlogic: add Odroid C4 support

Odroid C4 is an Amlogic SM1 device, the board config and board documentation
are adapted from the Odroid-N2 support from the same vendor.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
[narmstrong: fix odroid-c4.rst typos and structure]
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Anand Moon <linux.amoon@gmail.com>
diff --git a/doc/board/amlogic/index.rst b/doc/board/amlogic/index.rst
index 3730419..0e2f8c9 100644
--- a/doc/board/amlogic/index.rst
+++ b/doc/board/amlogic/index.rst
@@ -17,7 +17,7 @@
 +===============================+===========+==============+==============+============+============+=============+==============+
 | Boards               		| Odroid-C2 | P212         | Khadas VIM2  | S400       | U200       | Odroid-N2   | SEI610       |
 |				| Nanopi-K2 | Khadas-VIM   | Libretech-PC |	       | SEI510	    | Khadas-VIM3 | Khadas-VIM3L |
-|				| P200	    | LibreTech-CC |	          |	       |            |	          |    	         |
+|				| P200	    | LibreTech-CC |	          |	       |            |	          | Odroid-C4    |
 |				| P201	    | LibreTech-AC |	          |	       |            |             |    	         |
 +-------------------------------+-----------+--------------+--------------+------------+------------+-------------+--------------+
 | UART               		| **Yes**   | **Yes**      | **Yes**      | **Yes**    | **Yes**    | **Yes**     | **Yes**      |
@@ -83,6 +83,7 @@
    libretech-cc
    nanopi-k2
    odroid-c2
+   odroid-c4
    odroid-n2
    p200
    p201
diff --git a/doc/board/amlogic/odroid-c4.rst b/doc/board/amlogic/odroid-c4.rst
new file mode 100644
index 0000000..5a5a868
--- /dev/null
+++ b/doc/board/amlogic/odroid-c4.rst
@@ -0,0 +1,134 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+U-Boot for ODROID-C4
+====================
+
+ODROID-C4 is a single board computer manufactured by Hardkernel
+Co. Ltd with the following specifications:
+
+ - Amlogic S905X3 Arm Cortex-A55 quad-core SoC
+ - 4GB DDR4 SDRAM
+ - Gigabit Ethernet
+ - HDMI 2.1 display
+ - 40-pin GPIO header
+ - 4x USB 3.0 Host
+ - 1x USB 2.0 Host/OTG (micro)
+ - eMMC, microSD
+ - UART serial
+ - Infrared receiver
+
+Schematics are available on the manufacturer website.
+
+U-Boot compilation
+------------------
+
+.. code-block:: bash
+
+    $ export CROSS_COMPILE=aarch64-none-elf-
+    $ make odroid-c4_defconfig
+    $ make
+
+Image creation
+--------------
+
+Amlogic doesn't provide sources for the firmware and for tools needed
+to create the bootloader image, so it is necessary to obtain them from
+the git tree published by the board vendor:
+
+.. code-block:: bash
+
+    $ wget https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-aarch64-none-elf-4.8-2013.11_linux.tar.xz
+    $ wget https://releases.linaro.org/archive/13.11/components/toolchain/binaries/gcc-linaro-arm-none-eabi-4.8-2013.11_linux.tar.xz
+    $ tar xvfJ gcc-linaro-aarch64-none-elf-4.8-2013.11_linux.tar.xz
+    $ tar xvfJ gcc-linaro-arm-none-eabi-4.8-2013.11_linux.tar.xz
+    $ export PATH=$PWD/gcc-linaro-aarch64-none-elf-4.8-2013.11_linux/bin:$PWD/gcc-linaro-arm-none-eabi-4.8-2013.11_linux/bin:$PATH
+
+    $ DIR=odroid-c4
+    $ git clone --depth 1 \
+       https://github.com/hardkernel/u-boot.git -b odroidg12-v2015.01 \
+       $DIR
+
+    $ cd odroid-c4
+    $ make odroidc4_defconfig
+    $ make
+    $ export UBOOTDIR=$PWD
+
+Go back to mainline U-Boot source tree then :
+
+.. code-block:: bash
+
+    $ mkdir fip
+
+    $ wget https://github.com/BayLibre/u-boot/releases/download/v2017.11-libretech-cc/blx_fix_g12a.sh -O fip/blx_fix.sh
+    $ cp $UBOOTDIR/build/scp_task/bl301.bin fip/
+    $ cp $UBOOTDIR/build/board/hardkernel/odroidc4/firmware/acs.bin fip/
+    $ cp $UBOOTDIR/fip/g12a/bl2.bin fip/
+    $ cp $UBOOTDIR/fip/g12a/bl30.bin fip/
+    $ cp $UBOOTDIR/fip/g12a/bl31.img fip/
+    $ cp $UBOOTDIR/fip/g12a/ddr3_1d.fw fip/
+    $ cp $UBOOTDIR/fip/g12a/ddr4_1d.fw fip/
+    $ cp $UBOOTDIR/fip/g12a/ddr4_2d.fw fip/
+    $ cp $UBOOTDIR/fip/g12a/diag_lpddr4.fw fip/
+    $ cp $UBOOTDIR/fip/g12a/lpddr3_1d.fw fip/
+    $ cp $UBOOTDIR/fip/g12a/lpddr4_1d.fw fip/
+    $ cp $UBOOTDIR/fip/g12a/lpddr4_2d.fw fip/
+    $ cp $UBOOTDIR/fip/g12a/piei.fw fip/
+    $ cp $UBOOTDIR/fip/g12a/aml_ddr.fw fip/
+    $ cp u-boot.bin fip/bl33.bin
+
+    $ sh fip/blx_fix.sh \
+    	fip/bl30.bin \
+    	fip/zero_tmp \
+    	fip/bl30_zero.bin \
+    	fip/bl301.bin \
+    	fip/bl301_zero.bin \
+    	fip/bl30_new.bin \
+    	bl30
+
+    $ sh fip/blx_fix.sh \
+    	fip/bl2.bin \
+    	fip/zero_tmp \
+    	fip/bl2_zero.bin \
+    	fip/acs.bin \
+    	fip/bl21_zero.bin \
+    	fip/bl2_new.bin \
+    	bl2
+
+    $ $UBOOTDIR/fip/g12a/aml_encrypt_g12a --bl30sig --input fip/bl30_new.bin \
+    					--output fip/bl30_new.bin.g12a.enc \
+    					--level v3
+    $ $UBOOTDIR/fip/g12a/aml_encrypt_g12a --bl3sig --input fip/bl30_new.bin.g12a.enc \
+    					--output fip/bl30_new.bin.enc \
+    					--level v3 --type bl30
+    $ $UBOOTDIR/fip/g12a/aml_encrypt_g12a --bl3sig --input fip/bl31.img \
+    					--output fip/bl31.img.enc \
+    					--level v3 --type bl31
+    $ $UBOOTDIR/fip/g12a/aml_encrypt_g12a --bl3sig --input fip/bl33.bin --compress lz4 \
+    					--output fip/bl33.bin.enc \
+    					--level v3 --type bl33 --compress lz4
+    $ $UBOOTDIR/fip/g12a/aml_encrypt_g12a --bl2sig --input fip/bl2_new.bin \
+    					--output fip/bl2.n.bin.sig
+    $ $UBOOTDIR/fip/g12a/aml_encrypt_g12a --bootmk \
+    		--output fip/u-boot.bin \
+    		--bl2 fip/bl2.n.bin.sig \
+    		--bl30 fip/bl30_new.bin.enc \
+    		--bl31 fip/bl31.img.enc \
+    		--bl33 fip/bl33.bin.enc \
+    		--ddrfw1 fip/ddr4_1d.fw \
+    		--ddrfw2 fip/ddr4_2d.fw \
+    		--ddrfw3 fip/ddr3_1d.fw \
+    		--ddrfw4 fip/piei.fw \
+    		--ddrfw5 fip/lpddr4_1d.fw \
+    		--ddrfw6 fip/lpddr4_2d.fw \
+    		--ddrfw7 fip/diag_lpddr4.fw \
+    		--ddrfw8 fip/aml_ddr.fw \
+    		--ddrfw9 fip/lpddr3_1d.fw \
+    		--level v3
+
+and then write the image to SD with:
+
+.. code-block:: bash
+
+    $ DEV=/dev/your_sd_device
+    $ dd if=fip/u-boot.bin.sd.bin of=$DEV conv=fsync,notrunc bs=512 skip=1 seek=1
+    $ dd if=fip/u-boot.bin.sd.bin of=$DEV conv=fsync,notrunc bs=1 count=444