IMX_USR2_RDR
while (ISSET(bus_space_read_4(iot, ioh, IMX_USR2), IMX_USR2_RDR)
if (usr2 & IMX_USR2_RDR)
} while (usr2 & (IMX_USR2_RDR|IMX_USR2_BRCD));
if (!(usr2 & IMX_USR2_RDR))
while (!((usr2 = bus_space_read_4(iot, ioh, IMX_USR2)) & IMX_USR2_RDR))
((usr2 = bus_space_read_4(iot, ioh, IMX_USR2)) & IMX_USR2_RDR)) {
#define IMXUART_RXINTR_USR2 (IMX_USR2_IDLE|IMX_USR2_RDR)