dt-bindings: trivial-devices: add arduino spi mcu interface

Add unoq mcu interface. It describes an iterface between Qualcomm
QRB2210 microprocessor and STMicroelectronics STM32U585 microcontroller
on Arduino UnoQ single-board computer.
This is a trivial device since it's usage is handled in user space
by the arduino-router service.

Signed-off-by: Riccardo Mereu <r.mereu@arduino.cc>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://patch.msgid.link/20251120155825.121483-3-r.mereu.kernel@arduino.cc
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: SuMere

Documentation/devicetree/bindings/trivial-devices.yaml

@@ -53,6 +53,8 @@ properties:
           - adi,lt7182s
             # AMS iAQ-Core VOC Sensor
           - ams,iaq-core
+            # Arduino microcontroller interface over SPI on UnoQ board
+          - arduino,unoq-mcu
             # Temperature monitoring of Astera Labs PT5161L PCIe retimer
           - asteralabs,pt5161l
             # i2c h/w elliptic curve crypto module