INT_TIMEOUT
bus_space_write_4(iot, ioh, UART_CHNL_INT_STS, INT_TIMEOUT);
uint32_t mask = INT_TIMEOUT | INT_PARE | INT_FRAME | INT_ROVR | INT_RFUL | INT_RTRIG;
return (irq_polling(FDC_IRQ, INT_TIMEOUT)); /* wait interrupt */