NI16550_PMR_MODE_MASK
u8 pmr_mode = pmr & NI16550_PMR_MODE_MASK;
#define NI16550_PMR_MODE_RS232 FIELD_PREP(NI16550_PMR_MODE_MASK, 0) /* currently 232 */
#define NI16550_PMR_MODE_RS485 FIELD_PREP(NI16550_PMR_MODE_MASK, 1) /* currently 485 */