Documentation: Add XIAO RA4M1 Board

Added documentation for Seeed Studio XIAO RA4M1
Board.

Signed-off-by: Rodrigo Sim <rcsim10@gmail.com>

Documentation/platforms/arm/ra4m1/boards/xiao-ra4m1/index.rst

@@ -0,0 +1,151 @@
+=======================
+Seeed Studio XIAO RA4M1
+=======================
+
+The `Seeed Studio XIAO RA4M1 <https://wiki.seeedstudio.com/getting_started_xiao_ra4m1/>`_ is a general purpose board supplied by
+Seeed Studio and it is compatible with the Renesas RA4M1 ecosystem, sharing the same MCU as Arduino R4 Minima
+(R7FA4M1AB3CFM).
+
+.. figure:: xiao-ra4m1.jpg
+   :align: center
+
+Features
+========
+
+* Renesas RA4M1, ARM® Dual Cortex-M4 @ 48MHz
+* 32kB SRAM, 256KkB Flash, 8KB EEPROM
+* Security: AES128/256
+* USB Type-C interface
+* 19 Pins:14x Analog,19x Digital, 2x IIC, 2x UART, 2x SPI
+* 1 user LED, 1 power LED，1 RGB LED (WS2812)
+* 1 RESET button, 1 BOOT button
+
+Serial Console
+==============
+
+By default, a serial console appears on pins 6 (TX GPIO) and pin 7
+(RX GPIO).  This console runs a 115200-8N1.
+
+User LED
+========
+
+The USER LED, the yellow LED on the XIAO RA4M1, is connected to P011
+according to the schematic diagram.
+
+Buttons
+=======
+
+The RESET and BOOT buttons can be used to enter "Renesas RA USB Boot" mode by
+reboot the board with BOOT shorted to GND and press the reset button twice (double click).
+The board will enumerate as "Renesas RA USB Boot".
+
+Pin Mapping
+===========
+Pads numbered anticlockwise from USB connector.
+
+===== ========== ==========
+Pad   Signal     Notes
+===== ========== ==========
+0     P014       D0/A0
+1     P000       D1/A1
+2     P001       D2/A2
+3     P002       D3/A3
+4     P006       D4/SDA
+5     P100       D5/SCL
+6     P301       D6/Default TX for UART0 serial console
+7     P301       D7/Default RX for UART0 serial console
+8     P111       D8/SCK
+9     P110       D9/MISO
+10    P109       D10/MOSI
+11    3V3        Power output to peripherals
+12    Ground
+13    VIN        +5V Supply to board
+===== ========== ==========
+
+Power Supply
+============
+The working voltage of the MCU is 3.3V. Voltage input connected to
+general I/O pins may cause chip damage if it’s higher than 3.3V.
+
+Installation
+============
+
+1. Configure and build NuttX:
+
+.. code-block:: console
+
+  $ git clone https://github.com/apache/nuttx.git nuttx
+  $ git clone https://github.com/apache/nuttx-apps.git apps
+  $ cd nuttx
+  $ make distclean
+  $ ./tools/configure.sh xiao-ra4m1:nsh
+  $ make V=1
+
+2. Connect the Seeed Studio XIAO RA4M1, and enter "Renesas RA USB Boot" mode,
+then, flash the ``nuttx.hex`` file using ``rfp-cli``:
+(https://www.renesas.com/en/software-tool/renesas-flash-programmer-programming-gui)
+
+Example command:
+
+.. code-block:: bash
+
+    rfp-cli -device ra -port /dev/ttyACM0 -p ./build/nuttx.hex
+
+3. To access the console, TX and RX pins must be connected to the
+   device such as USB-serial converter.
+
+Configurations
+==============
+
+nsh
+---
+Basic NuttShell configuration (console enabled in UART0, at 115200 bps).
+
+combo
+-----
+This configuration enabled NuttShell via Serial and enabled led and gpio
+examples:
+
+Testing leds:
+
+.. code-block:: console
+
+  $nsh> leds
+  leds_main: Starting the led_daemon
+  leds_main: led_daemon started
+
+  led_daemon (pid# 5): Running
+  led_daemon: Opening /dev/userleds
+  led_daemon: Supported LEDs 0x01
+  led_daemon: LED set 0x01
+  $nsh> led_daemon: LED set 0x00
+  led_daemon: LED set 0x01
+  led_daemon: LED set 0x00
+  led_daemon: LED set 0x01
+  led_daemon: LED set 0x00
+  led_daemon: LED set 0x01
+
+Testing gpios:
+
+========   ======   ==========
+PIN/GPIO    Mode      Device
+========   ======   ==========
+D0/P014    Input    /dev/gpio0
+D1/P000    Output   /dev/gpio1
+========   ======   ==========
+
+.. code-block:: console
+
+  $nsh> gpio /dev/gpio0
+  Driver: /dev/gpio0
+    Input pin:     Value=0
+  $nsh> gpio /dev/gpio0
+  Driver: /dev/gpio0
+    Input pin:     Value=1
+
+
+
+
+
+
+