portenta_c33: add initial documentation

Will complete the supported peripheral list and description later

Signed-off-by: Martino Facchin <m.facchin@arduino.cc>

boards/arduino/portenta_c33/doc/index.rst

@@ -0,0 +1,129 @@
+.. zephyr:board:: arduino_portenta_c33
+
+Overview
+********
+
+The Portenta C33 is a powerful System-on-Module based on the Renesas RA6M5
+microcontroller group, which utilizes the high-performance Arm® Cortex®-M33
+core. The Portenta C33 shares the same form factor as the Portenta H7 and is
+backward compatible with it, making it fully compatible with all Portenta
+family shields and carriers through its High-Density connectors.
+
+Hardware
+********
+
+- Renesas RA6M5 ARM Cortex-M33 processor at 200 MHz
+- 24 MHz crystal oscillator
+- 32.768 kHz crystal oscillator for RTC
+- 2 MB flash memory and 512 KiB of RAM
+- 16 MB external QSPI flash
+- One RGB user LED
+- One reset button
+- NXP SE050 secure element
+- Onboard 10/100 Ethernet PHY
+- WiFi + Bluetooth via ESP32-C3 running `esp-hosted`_ firmware
+- Battery charger
+- MKR header connector exposing standard peripherals (UART, SPI, I2C, ADC, PWM)
+- 160 pins high density Portenta connectors exposing SD, CAN, I2S, SWD interfaces
+
+Supported Features
+==================
+
+.. zephyr:board-supported-hw::
+
+Connections and IOs
+===================
+
+The `Arduino store`_ has detailed information about board connections. Download
+the `Arduino Portenta C33 Schematic`_ for more details.
+
+Serial Port
+===========
+
+The Portenta C33 exposes 4 serial ports with hardware flow control.
+
+PWM
+===
+
+The Portenta C33 exposes 10 dedicated independent PWM pins.
+
+USB Device Port
+===============
+
+The RA6M5 MCU has an high speed USB device port that can be used to communicate
+with a host PC.  See the :zephyr:code-sample-category:`usb` sample applications for
+more, such as the :zephyr:code-sample:`usb-cdc-acm` sample which sets up a virtual
+serial port that echos characters back to the host PC.
+A second full speed USB interface is exposed on the high density connectors.
+
+DAC
+===
+
+The RA6M5 MCU has two DACs with 12 bits of resolution. On the
+Arduino Portenta C33, the DACs are available on pins A5 and A6.
+
+Programming and Debugging
+*************************
+
+.. zephyr:board-supported-runners::
+
+The Arduino Portenta C33 ships with a DFU compatible bootloader. The
+bootloader can be entered by quickly tapping the reset button twice.
+
+Flashing
+========
+
+#. Build the Zephyr kernel and the :zephyr:code-sample:`hello_world` sample application:
+
+   .. zephyr-app-commands::
+      :zephyr-app: samples/hello_world
+      :board: arduino_portenta_c33
+      :goals: build
+      :compact:
+
+#. Connect the Portenta C33 to your host computer using USB
+
+#. Connect a 3.3 V USB to serial adapter to the board and to the
+   host.  See the `Serial Port`_ section above for the board's pin
+   connections.
+
+#. Run your favorite terminal program to listen for output. Under Linux the
+   terminal should be :code:`/dev/ttyACM0`. For example:
+
+   .. code-block:: console
+
+      $ minicom -D /dev/ttyACM0 -o
+
+   The -o option tells minicom not to send the modem initialization
+   string. Connection should be configured as follows:
+
+   - Speed: 115200
+   - Data: 8 bits
+   - Parity: None
+   - Stop bits: 1
+
+#. Tap the reset button twice quickly to enter bootloader mode
+
+#. Flash the image:
+
+   .. zephyr-app-commands::
+      :zephyr-app: samples/hello_world
+      :board: arduino_portenta_c33
+      :goals: flash
+      :compact:
+
+   You should see "Hello World! arduino_portenta_c33" in your terminal.
+
+References
+**********
+
+.. target-notes::
+
+.. _Arduino Store:
+    https://store.arduino.cc/products/portenta-c33
+
+.. _Arduino Portenta C33 Schematic:
+    http://docs.arduino.cc/resources/schematics/ABX00074-schematics.pdf
+
+.. _esp-hosted:
+    https://github.com/espressif/esp-hosted