boards: amlogic: update documentation for Beelink GT-King/Pro

Update the device matrix and add build instructions.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/doc/board/amlogic/beelink-gtking.rst b/doc/board/amlogic/beelink-gtking.rst
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+.. SPDX-License-Identifier: GPL-2.0+
+
+U-Boot for Beelink GT-King
+==========================
+
+The Shenzen AZW (Beelink) GT-King is based on the Amlogic W400 reference
+board with an S922X-H chip.
+
+- 4GB LPDDR4 RAM
+- 64GB eMMC storage
+- 10/100/1000 Base-T Ethernet
+- AP6356S Wireless (802.11 a/b/g/n/ac, BT 4.1)
+- HDMI 2.1 video
+- S/PDIF optical output
+- Analogue audio output
+- 1x USB 2.0 port
+- 2x USB 3.0 ports
+- IR receiver
+- 1x micro SD card slot
+
+Beelink do not provide public schematics, but have been willing
+to share them with known distro developers on request.
+
+U-Boot compilation
+------------------
+
+.. code-block:: bash
+
+    $ export CROSS_COMPILE=aarch64-none-elf-
+    $ make beelink-gtking_defconfig
+    $ make
+
+Image creation
+--------------
+
+Amlogic does not provide sources for the firmware and for tools needed
+to create the bootloader image. Beelink have provided the Amlogic "SDK"
+in their forums, but the u-boot sources included result in 2GB RAM being
+detected. The following FIPs were generated with newer private sources
+and give correct (4GB) RAM detection:
+
+https://github.com/LibreELEC/amlogic-boot-fip/tree/master/beelink-s922x
+
+NB: Beelink use a common board config for GT-King, GT-King Pro and the
+GS-King-X model, hence the "beelink-s922x" name.
+
+.. code-block:: bash
+
+    $ wget https://github.com/LibreELEC/amlogic-boot-fip/archive/master.zip
+    $ unzip master.zip
+    $ export FIPDIR=$PWD/amlogic-boot-fip/beelink-s922x
+
+Go back to the mainline U-Boot source tree then:
+
+.. code-block:: bash
+
+    $ mkdir fip
+    $ cp $FIPDIR/* 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
+
+    $ fip/aml_encrypt_g12b --bl30sig --input fip/bl30_new.bin \
+    				--output fip/bl30_new.bin.g12a.enc \
+    				--level v3
+    $ fip/aml_encrypt_g12b --bl3sig --input fip/bl30_new.bin.g12a.enc \
+    				--output fip/bl30_new.bin.enc \
+    				--level v3 --type bl30
+    $ fip/aml_encrypt_g12b --bl3sig --input fip/bl31.img \
+    				--output fip/bl31.img.enc \
+    				--level v3 --type bl31
+    $ fip/aml_encrypt_g12b --bl3sig --input fip/bl33.bin --compress lz4 \
+    				--output fip/bl33.bin.enc \
+    				--level v3 --type bl33
+    $ fip/aml_encrypt_g12b --bl2sig --input fip/bl2_new.bin \
+    				--output fip/bl2.n.bin.sig
+    $ fip/aml_encrypt_g12b --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 \
+    		--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