* ARM AMBA Primecell PL011 & PL010 serial UART

Required properties:
- compatible: must be "arm,primecell", "arm,pl011" or "arm,pl010"
- reg: exactly one register range with length 0x1000
- clock: input clock frequency for the UART (used to calculate the baud
  rate divisor)

Optional properties:
- skip-init: if present, the baud rate divisor is not changed
