IMX_USR1_AGTIM
bus_space_write_4(iot, ioh, IMX_USR1, IMX_USR1_AGTIM);
#define IMXUART_RXINTR_USR1 (IMX_USR1_RRDY|IMX_USR1_RXDS|IMX_USR1_AGTIM)
#define IMXUART_RXDMA_USR1 (IMX_USR1_RRDY|IMX_USR1_AGTIM)