doc: board: phytec: Add phyGATE-Tauri board documentation

Add brief documentation on how to build a bootable U-Boot image for the
phyGATE-Tauri-L.

Signed-off-by: Yannic Moog <y.moog@phytec.de>
Reviewed-by: Teresa Remmet <t.remmet@phytec.de>

board/phytec/phycore_imx8mm/MAINTAINERS

@@ -10,4 +10,6 @@ F:	arch/arm/dts/imx8mm-phygate-tauri-l-u-boot.dtsi
 F:      board/phytec/phycore_imx8mm/
 F:	configs/imx8mm-phygate-tauri-l_defconfig
 F:      configs/phycore-imx8mm_defconfig
+F:	doc/board/phytec/imx8mm-phygate-tauri-l.rst
+F:	doc/board/phytec/index.rst
 F:      include/configs/phycore_imx8mm.h

doc/board/phytec/imx8mm-phygate-tauri-l.rst

@@ -0,0 +1,60 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+phyGATE-Tauri-L-i.MX 8M Mini
+============================
+
+The phyGATE-Tauri-L-i.MX 8M Mini with 2GB of main memory is supported.
+
+Quick Start
+-----------
+
+- Build the ARM Trusted firmware binary
+- Get ddr firmware
+- Build U-Boot
+- Boot
+
+Build the ARM Trusted firmware binary
+-------------------------------------
+
+.. code-block:: bash
+
+   $ git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
+   $ cd trusted-firmware-a
+   $ export CROSS_COMPILE=aarch64-linux-gnu
+   $ export IMX_BOOT_UART_BASE=0x30880000
+   $ make PLAT=imx8mm bl31
+
+Get the ddr firmware
+--------------------
+
+.. code-block:: bash
+
+   $ wget https://www.nxp.com/lgfiles/NMG/MAD/YOCTO/firmware-imx-8.23.bin
+   $ chmod +x firmware-imx-8.23.bin
+   $ ./firmware-imx-8.23.bin
+
+Build U-Boot for SD card
+------------------------
+
+Copy binaries
+^^^^^^^^^^^^^
+
+.. code-block:: bash
+
+   $ cp <TF-A dir>/build/imx8mm/release/bl31.bin .
+   $ cp firmware-imx-8.23/firmware/ddr/synopsys/lpddr4*.bin .
+
+Build U-Boot
+^^^^^^^^^^^^
+
+.. code-block:: bash
+
+   $ make imx8mm-phygate-tauri-l_defconfig
+   $ make flash.bin
+
+Flash SD card
+^^^^^^^^^^^^^
+
+.. code-block:: bash
+
+   $ sudo dd if=flash.bin of=/dev/sd[x] bs=1024 seek=33 conv=sync

doc/board/phytec/index.rst

@@ -6,5 +6,6 @@ PHYTEC
 .. toctree::
    :maxdepth: 2
 
+   imx8mm-phygate-tauri-l
    phycore-imx8mm
    phycore-imx8mp