board: purism: add the Purism Librem5 phone

Initial commit of Librem5 u-boot and SPL

Signed-off-by: Angus Ainslie <angus@akkea.ca>
Co-developed-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
Reviewed-by: Fabio Estevam <festevam@denx.de>

doc/board/index.rst

@@ -28,6 +28,7 @@ Board-specific doc
    nokia/index
    nxp/index
    openpiton/index
+   purism/index
    qualcomm/index
    rockchip/index
    samsung/index

doc/board/purism/index.rst

@@ -0,0 +1,9 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Purism SPC
+==========
+
+.. toctree::
+   :maxdepth: 2
+
+   librem5

doc/board/purism/librem5.rst

@@ -0,0 +1,60 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Librem5
+==========
+
+U-Boot for the Purism Librem5 phone
+
+Quick Start
+-----------
+
+- Build the ARM Trusted firmware binary
+- Get ddr and hdmi firmware
+- Build U-Boot
+
+Get and Build the ARM Trusted firmware
+--------------------------------------
+
+Note: srctree is U-Boot source directory
+Get ATF from: https://source.puri.sm/Librem5/arm-trusted-firmware
+branch: librem5
+
+.. code-block:: bash
+
+   $ make PLAT=imx8mq CROSS_COMPILE=aarch64-linux-gnu- bl31
+   $ cp build/imx8mq/release/bl31.bin $(builddir)
+
+Get the ddr and display port firmware
+-------------------------------------
+
+.. code-block:: bash
+
+   $ wget https://www.nxp.com/lgfiles/NMG/MAD/YOCTO/firmware-imx-8.15.bin
+   $ chmod +x firmware-imx-8.15.bin
+   $ ./firmware-imx-8.15.bin
+   $ cp firmware-imx-8.15/firmware/hdmi/cadence/signed_dp_imx8m.bin $(builddir)
+   $ cp firmware-imx-8.15/firmware/ddr/synopsys/lpddr4*.bin $(builddir)
+
+Build U-Boot
+------------
+
+.. code-block:: bash
+
+   $ export CROSS_COMPILE=aarch64-linux-gnu-
+   $ make librem5_defconfig
+   $ make ARCH=arm
+
+Burn the flash.bin
+------------------
+
+Use uuu to burn flash.bin. Power on the phone while holding vol+ to get it
+into uuu mode.
+
+.. code-block:: bash
+
+   $ git clone https://source.puri.sm/Librem5/librem5-devkit-tools.git
+   $ cd librem5-devkit-tools
+   $ cp $(builddir)/flash.bin files/u-boot-librem5.imx
+   $ uuu uuu_scripts/u-boot_flash_librem5.lst
+
+Reboot the phone.