Add Arch and Board Docs

Documentation/platforms/risc-v/sg2000/boards/duos/index.rst

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+============
+Milk-V Duo S
+============
+
+`Milk-V Duo S <https://milkv.io/duo-s>`_ is a RISC-V Single-Board Computer
+based on the SOPHGO SG2000 RISC-V SoC with T-Head C906 64-bit Main Processor,
+512 MB of SIP DRAM memory and 10M / 100M MAC PHY Ethernet.
+
+Features
+========
+
+- **System on Chip:** SOPHGO SG2000
+    - **CPU:** 
+        - 64-bit T-Head C906 1.0 GHz (Main Processor)
+        - 64-bit T-Head C906 700 MHz (Co-Processor)
+        - 64-bit Arm Cortex-A53 1.0 GHz (Alternate Main Processor)
+
+- **MCU:** 8051 with 6 KB SRAM
+- **Memory:** SIP DRAM 512 MB
+- **TPU:** 0.5 TOPS INT8
+- **Storage:** 1 x microSD Connector, 1 x eMMC Pad
+- **USB:** 1 x Type-C for Power and Data or 1x USB 2.0 A Port Host
+- **MIPI CSI:** 1 x 16P FPC Connector (MIPI CSI 2-Lane), 1 x 15P FPC Connector (MIPI CSI 2-Lane)	
+- **Sensor Support:** 5M @ 30 FPS
+- **MIPI DSI:** Via GPIO Header (MIPI DSI 4-Lane)	
+- **Ethernet:** 100 Mbps Ethernet Port (RJ45)
+- **Wireless:** Optional Wi-Fi 6 / Bluetooth 5
+- **Audio:** Via GPIO Pin	
+- **GPIO:** Up to 39 x GPIO Pin (via 2 x 26-Pin GPIO Header)
+- **Others:** 1 x Boot Switch, 1 x Recovery Key, 1 x Reset Key
+
+Serial Console
+==============
+
+A **USB Serial Adapter** is required to run NuttX on Milk-V Duo S,
+**CP2102** is recommended. CH340 might not work correctly with Milk-V Duo S.
+
+Connect the USB Serial Adapter to Milk-V Duo S Serial Console at:
+
+========== ================
+USB Serial Milk-V Duo S Pin
+========== ================
+GND        Pin 6 (GND)
+RX         Pin 8 (XGPIOA 16 / UART0 TX)
+TX         Pin 10 (XGPIOA 17 / UART0 RX)
+========== ================
+
+On the USB Serial Adapter, set the **Voltage Level** to 3V3.
+
+Connect Milk-V Duo S 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**.
+
+NuttX will appear in the Serial Console when it boots on Milk-V Duo S.
+
+RISC-V Toolchain
+================
+
+Before building NuttX for Milk-V Duo S, download the toolchain for
+`xPack GNU RISC-V Embedded GCC (riscv-none-elf) <https://github.com/xpack-dev-tools/riscv-none-elf-gcc-xpack/releases>`_.
+
+Add the downloaded toolchain ``xpack-riscv-none-elf-gcc-.../bin``
+to the ``PATH`` Environment Variable.
+
+Check the RISC-V Toolchain:
+
+.. code:: console
+
+   $ riscv-none-elf-gcc -v
+
+Building
+========
+
+To build NuttX for Milk-V Duo S, :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 duos:nsh
+   $ make
+   $ riscv-none-elf-objcopy -O binary nuttx nuttx.bin
+
+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-sg2000
+
+The NuttX Image ``Image-sg2000`` will be copied to the TFTP Server in the next step.
+
+Booting
+=======
+
+NuttX requires a microSD Card with U-Boot Bootloader. Prepare a
+`Linux microSD Card <https://lupyuen.github.io/articles/sg2000#download-the-linux-microsd>`_
+for Duo S.
+
+To boot NuttX on Milk-V Duo S, flip the `Main Processor Switch <https://milkv.io/docs/duo/getting-started/duos#risc-v-and-arm-switching>`_
+to **RV** (RISC-V).
+`Install a TFTP Server <https://lupyuen.github.io/articles/sg2000#boot-nuttx-over-tftp>`_
+on our computer.
+
+Copy the file ``Image-sg2000`` from the previous section to the TFTP Server,
+together with the Device Tree:
+
+.. code:: console
+
+   $ wget https://github.com/lupyuen2/wip-nuttx/releases/download/sg2000-1/cv181x_milkv_duos_sd.dtb
+   $ scp Image-sg2000 \
+      tftpserver:/tftpfolder/Image-sg2000
+   $ scp cv181x_milkv_duos_sd.dtb \
+      tftpserver:/tftpfolder/cv181x_milkv_duos_sd.dtb
+
+Check that Duo S is connected to our computer via a USB Serial Adapter at 115.2 kbps.
+
+Insert the microSD Card into Duo S, connect the Ethernet Port and power up via the USB-C Port.
+
+When Duo S boots, press Enter to see the U-Boot Prompt.
+Run these commands to `boot NuttX over TFTP <https://lupyuen.github.io/articles/sg2000#boot-nuttx-over-tftp>`_:
+
+.. code:: console
+
+   # Change to your TFTP Server
+   $ setenv tftp_server 192.168.x.x
+   $ saveenv
+   $ dhcp ${kernel_addr_r} ${tftp_server}:Image-sg2000
+   $ tftpboot ${fdt_addr_r} ${tftp_server}:cv181x_milkv_duos_sd.dtb
+   $ fdt addr ${fdt_addr_r}
+   $ booti ${kernel_addr_r} - ${fdt_addr_r}
+
+Or configure U-Boot to `boot NuttX automatically <https://lupyuen.github.io/articles/sg2000#boot-nuttx-over-tftp>`_.
+
+NuttX boots on Duo S 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 Milk-V Duo S supports these peripherals:
+
+======================== ======= =====
+Peripheral               Support NOTES
+======================== ======= =====
+UART                     Yes
+======================== ======= =====

Documentation/platforms/risc-v/sg2000/index.rst

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+=============
+SOPHGO SG2000
+=============
+
+`SOPHGO SG2000 <https://milkv.io/chips/sg2000>`_ is a 64-bit RISC-V SoC with 2 RISC-V Cores and 1 Arm Core:
+
+- **Main Processor:** T-Head C906 1.0 GHz 64-bit RISC-V Core
+    - 32 KB I-Cache, 64KB D-Cache
+    - Integrated Vector and Floating-Point Operation Unit (FPU)
+
+- **Co-Processor:** T-Head C906 700 MHz 64-bit RISC-V Core
+    - Integrated Floating-Point Unit (FPU)
+
+- **Alternate Main Processor:** Cortex-A53 1.0 GHz 64-bit Arm Core
+    - 32 KB I-Cache, 32 KB D-Cache
+    - 128 KB L2 Cache
+    - Support Neon and Floating-Point Operation Unit (FPU)
+
+- **MCU:** 8051 with 6 KB SRAM
+- **TPU:** 0.5 TOPS INT8
+- **Memory:** SIP DRAM 512 MB
+- **Video Module:** ISP 5M @ 30 FPS, 2L MIPI DSI 5M @ 30 FPS, 4L or 2L+2L MIPI CSI 5M @ 30 FPS, H.265 / H.264 Decoding and Encoding 5M @ 30 FPS
+- **Audio Module:** 16-bit Audio Codec, 2 x I2S / PCM, 1 x DMIC
+- **Storage:** SPI-NOR, SPI-NAND, eMMC 5.0, 2 x SDIO 3.0
+- **Network:** 10M / 100M MAC PHY
+- **Security Module:** Crypto, Secure Boot, TRNG, Efuse
+- **Peripherals:** 1 x USB 2.0 DRD, 5 x UART, 4 x SPI, 16 x PWM, 1 x IR, 6 x I2C, 6 x ADC, GPIOs
+
+Supported Boards
+================
+
+.. toctree::
+   :glob:
+   :maxdepth: 1
+
+   boards/*/*