Documentation/platforms/arm64/a527/boards/avaota-a1: Add support for PINE64 Yuzuki Avaota-A1 SBC (Allwinner A527 SoC)

This PR adds support for the PINE64 Yuzuki Avaota-A1 SBC,
based on Allwinner A527 Arm64 SoC.
Most of the code was derived from NuttX for
QEMU Arm64 Kernel Build qemu-armv8a:knsh.
The modified code is explained here:
https://lupyuen.github.io/articles/avaota#appendix-port-nuttx-to-avaota-a1

platforms/arm64/a527/index.rst:
  Added Avaota-A1 to Allwinner A527 SoC

platforms/arm64/a527/boards/avaota-a1/avaota-a1.jpg:
  Photo of Avaota-A1, taken by me

platforms/arm64/a527/boards/avaota-a1/index.rst:
  Building and booting NuttX for Avaota-A1

Signed-off-by: Lup Yuen Lee <luppy@appkaki.com>

Documentation/platforms/arm64/a527/boards/avaota-a1/index.rst

@@ -0,0 +1,151 @@
+=======================
+PINE64 Yuzuki Avaota-A1
+=======================
+
+`Avaota-A1 <https://pine64.com/product/yuzuki-avaota-a1-single-board-computer-2gb-16gb/>`_
+is an ARM64 Single-Board Computer based on the Allwinner A527 SoC.
+
+.. figure:: avaota-a1.jpg
+   :align: center
+
+Features
+========
+
+- **System on Chip:** Allwinner A527
+    - **CPU:** Octa-Core ARM Cortex-A55
+    - **GPU:** ARM G57 MC1
+    - **Interrupt Controller:** ARM GIC-600 (Generic Interrupt Controller v3)
+- **RAM:** 2GB or 4GB LPDDR4 SDRAM
+- **Internal Storage:** 16GB or 32GB eMMC
+- **External Storage:** MicroSD
+- **Ethernet:** Dual Gigabit Ports
+- **Wireless:** WiFi 6, Bluetooth 5.4
+- **I/O:** UART, SPI, I2C, USB 3.0 OTG
+
+Serial Console
+==============
+
+A **USB Serial Adapter** (CH340 or CP2102) is required to run NuttX.
+
+Connect the USB Serial Adapter to the Avaota-A1 Serial Console at:
+
+========== =================
+USB Serial Avaota-A1 Pin
+========== =================
+GND        Pin 6 (GND)
+RX         Pin 8 (UART0 TX)
+TX         Pin 10 (UART0 RX)
+========== =================
+
+On the USB Serial Adapter, set the **Voltage Level** to 3V3.
+
+Connect Avaota-A1 to our computer with the USB Serial Adapter.
+On our computer, start a Serial Terminal and connect to the USB Serial Port
+at **115.2 kbps**:
+
+.. code:: console
+
+   $ screen /dev/ttyUSB0 115200
+
+NuttX will appear in the Serial Console when it boots.
+
+ARM64 Toolchain
+===============
+
+Before building NuttX, download the toolchain for
+`xPack GNU AArch64 Embedded GCC (aarch64-none-elf) <https://github.com/xpack-dev-tools/aarch64-none-elf-gcc-xpack/releases>`_.
+
+Add the downloaded toolchain ``xpack-aarch64-none-elf-gcc-.../bin``
+to the ``PATH`` Environment Variable.
+
+Check the ARM64 Toolchain:
+
+.. code:: console
+
+   $ aarch64-none-elf-gcc -v
+
+Building
+========
+
+To build NuttX, :doc:`install the prerequisites </quickstart/install>` and
+:doc:`clone the git repositories </quickstart/install>` for ``nuttx`` and ``apps``.
+
+Configure the NuttX project and build the project:
+
+.. code:: console
+
+   $ cd nuttx
+   $ tools/configure.sh avaota-a1:nsh
+   $ make
+
+This produces the NuttX Kernel ``nuttx.bin``.  Next, build the NuttX Apps Filesystem:
+
+.. code:: console
+
+   $ make export
+   $ pushd ../apps
+   $ tools/mkimport.sh -z -x ../nuttx/nuttx-export-*.tar.gz
+   $ make import
+   $ popd
+   $ genromfs -f initrd -d ../apps/bin -V "NuttXBootVol"
+
+This generates the Initial RAM Disk ``initrd``.
+
+Package the NuttX Kernel and Initial RAM Disk into a NuttX Image:
+
+.. code:: console
+
+   $ head -c 65536 /dev/zero >/tmp/nuttx.pad
+   $ cat nuttx.bin /tmp/nuttx.pad initrd >Image
+
+The NuttX Image ``Image`` will be copied to a microSD Card in the next step.
+
+Booting
+=======
+
+NuttX boots on PinePhone via a microSD Card. To prepare the microSD Card, download the
+**AvaotaOS Image** ``AvaotaOS-...-noble-gnome-arm64-avaota-a1.img.xz`` from
+`github.com/AvaotaSBC/AvaotaOS <https://github.com/AvaotaSBC/AvaotaOS/releases>`_.
+
+Write the downloaded image to a microSD Card with
+`Balena Etcher <https://www.balena.io/etcher/>`_.
+
+Copy the file ``Image`` from the previous section
+and overwrite the file on the microSD Card.
+
+Check that Avaota-A1 is connected to our computer via a USB Serial Adapter at 115.2 kbps:
+
+.. code:: console
+
+   $ screen /dev/ttyUSB0 115200
+
+Insert the microSD Card into Avaota-A1 and power up.
+NuttX boots and NuttShell (nsh) appears in the Serial Console.
+
+To see the available commands in NuttShell:
+
+.. code:: console
+
+   $ help
+
+Configurations
+==============
+
+nsh
+---
+
+Basic configuration that runs NuttShell (nsh).
+This configuration is focused on low level, command-line driver testing.
+Built-in applications are supported, but none are enabled.
+Serial Console is enabled on UART0 at 115.2 kbps.
+
+Peripheral Support
+==================
+
+NuttX for Avaota-A1 supports these peripherals:
+
+======================== ======= =====
+Peripheral               Support NOTES
+======================== ======= =====
+UART                     Yes
+======================== ======= =====

Documentation/platforms/arm64/a527/index.rst

@@ -9,3 +9,12 @@ Allwinner A527
 - **Interrupt Controller:** ARM GIC-600 (Generic Interrupt Controller v3)
 - **RAM:** Up to 4GB LPDDR4 SDRAM
 - **I/O:** UART, SPI, I2C, USB 3.0 OTG, SDIO, Dual Gigabit Ethernet
+
+Supported Boards
+================
+
+.. toctree::
+   :glob:
+   :maxdepth: 1
+
+   boards/*/*