AUART_INTR_RTIS
mxs_clr(istat & (AUART_INTR_RTIS | AUART_INTR_TXIS | AUART_INTR_RXIS
if (istat & (AUART_INTR_RTIS | AUART_INTR_RXIS)) {
istat &= ~(AUART_INTR_RTIS | AUART_INTR_RXIS);