RXSTAT_OVERRUN
if (rxs & RXSTAT_OVERRUN)
uart_insert_char(port, rxs, RXSTAT_OVERRUN, ch, flag);
port->read_status_mask = RXSTAT_OVERRUN;
port->ignore_status_mask |= RXSTAT_OVERRUN;
#define RXSTAT_ANYERR (RXSTAT_FRAME|RXSTAT_PARITY|RXSTAT_OVERRUN)