[PATCH v4 7/7] docs/system/riscv: Add Milk-V Duo board documentation

Add documentation for the Milk-V Duo board. This includes a brief
overview of the hardware, a list of supported devices, and practical
instructions on how to boot the machine using OpenSBI and a Linux
kernel with an emulated SD card.

Signed-off-by: Kuan-Wei Chiu <[email protected]>
---
 MAINTAINERS                     |  1 +
 docs/system/riscv/milkv-duo.rst | 49 +++++++++++++++++++++++++++++++++
 docs/system/target-riscv.rst    |  1 +
 3 files changed, 51 insertions(+)
 create mode 100644 docs/system/riscv/milkv-duo.rst

diff --git a/MAINTAINERS b/MAINTAINERS
index 3f79334c59..9750a39ca3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1854,6 +1854,7 @@ F: tests/qtest/k230-wdt-test.c
 Milk-V Duo
 M: Kuan-Wei Chiu <[email protected]>
 S: Maintained
+F: docs/system/riscv/milkv-duo.rst
 F: hw/char/dw8250.c
 F: hw/misc/cv1800b_clk.c
 F: hw/riscv/cv1800b.c
diff --git a/docs/system/riscv/milkv-duo.rst b/docs/system/riscv/milkv-duo.rst
new file mode 100644
index 0000000000..1758db2c1e
--- /dev/null
+++ b/docs/system/riscv/milkv-duo.rst
@@ -0,0 +1,49 @@
+Milk-V Duo board (``milkv-duo``)
+================================
+
+The ``milkv-duo`` machine is compatible with the Milk-V Duo development board.
+
+The Milk-V Duo is an ultra-compact embedded development platform based on the
+Sophgo CV1800B SoC. The CV1800B features T-Head C906 RISC-V processing cores
+along with integrated peripherals.
+
+For more information, see <https://milkv.io/duo>
+
+Supported devices
+-----------------
+The ``milkv-duo`` machine supports the following devices:
+
+* T-Head C906 cores
+* Core Local Interruptor (CLINT)
+* Platform-Level Interrupt Controller (PLIC)
+* DesignWare APB UART (dw8250)
+* SDHCI controller
+* CV1800B clock controller
+
+Boot options
+------------
+The ``milkv-duo`` machine supports direct boot using a generic RISC-V OpenSBI
+firmware and a Linux kernel. The root filesystem can be provided via the
+emulated SD card.
+
+Running
+-------
+To boot the machine, you need a Linux kernel (built with CV1800B support), a
+device tree blob (DTB), and a root filesystem image (e.g., built via BusyBox
+or Buildroot).
+
+Use the following command to boot the system directly to the Linux shell:
+
+.. code-block:: bash
+
+   $ qemu-system-riscv64 -M milkv-duo -nographic \
+      -bios pc-bios/opensbi-riscv64-generic-fw_dynamic.bin \
+      -dtb /path/to/linux/arch/riscv/boot/dts/sophgo/cv1800b-milkv-duo.dtb \
+      -kernel /path/to/linux/arch/riscv/boot/Image \
+      -drive file=/path/to/rootfs.ext4,format=raw,id=sd-card \
+      -device sd-card,drive=sd-card \
+      -append "console=ttyS0,115200 root=/dev/mmcblk0 rootwait earlycon"
+
+This command boots the generic OpenSBI firmware, loads the Linux Image and the
+specified DTB, and mounts the ext4 root filesystem from the emulated SD card.
+The console output is routed to the ``ttyS0`` serial port.
diff --git a/docs/system/target-riscv.rst b/docs/system/target-riscv.rst
index 2639866a3e..1e49055e29 100644
--- a/docs/system/target-riscv.rst
+++ b/docs/system/target-riscv.rst
@@ -69,6 +69,7 @@ undocumented; you can get a complete list by running
    riscv/k230
    riscv/microblaze-v-generic
    riscv/microchip-icicle-kit
+   riscv/milkv-duo
    riscv/mips
    riscv/shakti-c
    riscv/sifive_u
-- 
2.55.0.766.g2966f0265a-goog