dt-bindings: serial: allow onewire as child node

The UART 1-Wire bus utilizes the Serial Device Bus to create the 1-wire
timing patterns.

Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Christoph Winklhofer <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>

Documentation/devicetree/bindings/serial/serial.yaml

···
       TX FIFO threshold configuration (in bytes).
 
 patternProperties:
-  "^(bluetooth|bluetooth-gnss|gnss|gps|mcu)$":
+  "^(bluetooth|bluetooth-gnss|gnss|gps|mcu|onewire)$":
     if:
       type: object
     then: