Sandbox serial

The sandbox serial device is an emulated device which displays its output
on the host machine's console, and accepts input from its keyboard.

Required properties:
  compatible: "sandbox,serial"

Optional properties:
  sandbox,text-colour: If present, this is the colour of the console text.
        Supported values are:
        "black", "red", "green", "yellow", "blue", "megenta", "cyan",
        "white"
