boards/devebox-stm32h743: add board documentation

Documentation for the DevEbox STM32H743 board covering pin mappings,
configurations, and flashing instructions.

Signed-off-by: Andrey Sobol <andrey.sobol.nn@gmail.com>

Documentation/platforms/arm/stm32h7/boards/devebox-stm32h743/index.rst

@@ -0,0 +1,187 @@
+==================
+devebox-stm32h743
+==================
+
+.. tags:: chip:stm32, chip:stm32h7, chip:stm32h743
+
+NuttX port for the DevEbox STM32H743 board.
+
+.. figure:: devebox-stm32h743-top.jpg
+   :align: center
+   :width: 80%
+
+|
+
+.. figure:: devebox-stm32h743-bottom.jpg
+   :align: center
+   :width: 80%
+
+|
+
+Board information
+=================
+
+The DevEbox STM32H743 board is developed based on the STM32H743VI microcontroller.
+
+Board information: https://stm32-base.org/boards/STM32H743VIT6-STM32H7XX-M
+
+The board features:
+
+  - USB-C power supply
+  - SWD connector
+  - Crystal for HS 25MHz
+  - Crystal for RTC 32.768KHz
+  - 1 user LED (PA1)
+  - 2 user buttons (PE3, PC5)
+  - 1 MicroSD connector supporting 1 or 4-bit bus (SDMMC1)
+  - 1 USB 2.0 OTG FS
+  - 1 QSPI Flash W25Q64 (8MB)
+
+Serial Console
+==============
+
+The board uses USART1 for the serial debug console.
+
+======== =====
+USART1   PINS
+======== =====
+TX       PA9
+RX       PA10
+======== =====
+
+**Note:** PA10 is also used as OTGFS_ID. When USB is enabled,
+``CONFIG_OTG_ID_GPIO_DISABLE=y`` must be set to avoid a pin conflict.
+
+LED
+===
+
+The board has one software-controllable LED on PA1 (active low).
+
+Board buttons
+=============
+
+The board has two buttons with active-low logic:
+
+==== =====
+ID   GPIO
+==== =====
+K1   PE3
+K2   PC5
+==== =====
+
+SDMMC
+=====
+
+The board has one microSD slot connected via SDMMC1.
+
+=========== =====
+SDMMC1      PINS
+=========== =====
+SDMMC_D0    PC8
+SDMMC_D1    PC9
+SDMMC_D2    PC10
+SDMMC_D3    PC11
+SDMMC_CK    PC12
+SDMMC_CMD   PD2
+=========== =====
+
+=============== =====
+GPIO            PINS
+=============== =====
+SDCARD_DETECT   PD4
+=============== =====
+
+QSPI Flash
+==========
+
+The board has a W25Q64 (8MB) QSPI NOR Flash.
+
+========= =====
+QSPI      PINS
+========= =====
+BK1_CS    PB6
+BK1_IO0   PD11
+BK1_IO1   PD12
+BK1_IO2   PE2
+BK1_IO3   PD13
+CLK       PB2
+========= =====
+
+USB OTG FS
+==========
+
+========= =====
+OTG_FS    PINS
+========= =====
+DM        PA11
+DP        PA12
+ID        PA10
+========= =====
+
+Flashing
+========
+
+The board can be flashed via the SWD connector using a compatible programmer
+such as J-Link, ST-Link, or other SWD probe.
+
+SWD
+---
+
+Connect the SWD programmer as follows:
+
+================ ===============
+SWD Programmer   DevEbox
+================ ===============
+SWDIO            DIO
+GND              GND
+SWCLK            CLK
+3.3V             3V3
+================ ===============
+
+J-Link example::
+
+  JLinkExe -autoconnect 1 -device STM32H743VI -if SWD -speed 4000 \
+    -CommanderScript flash.jlink
+
+With flash.jlink::
+
+  reset
+  halt
+  loadfile nuttx.bin 0x08000000
+  reset
+  go
+  exit
+
+Configurations
+==============
+
+Each devebox-stm32h743 configuration is maintained in a sub-directory and
+can be selected as follows::
+
+  ./tools/configure.sh devebox-stm32h743:<subdir>
+
+Where ``<subdir>`` is one of the following:
+
+nsh
+---
+
+Configures the NuttShell (nsh) with a serial console on USART1 (PA9/PA10).
+Minimal configuration suitable for basic testing.
+
+nsh+debug
+---------
+
+nsh configuration with debug features enabled (assertions, LEDs, stack
+checking, RAMLOG). Syslog output goes to ``/dev/ttyRAM`` via RAMLOG.
+
+full
+----
+
+All-in-one configuration enabling all board features:
+
+  - SD card (``/dev/mmcsd0``)
+  - USB CDC ACM (``/dev/ttyACM0``)
+  - W25Q64 QSPI Flash NXFFS (``/w25``)
+  - Buttons (``/dev/buttons``)
+  - RAMLOG (``/dev/ttyRAM``)
+  - GPIO helper (``/dev/gpio*``)