UART_DR
c = bus_space_read_2(iot, ioh, UART_DR);
bus_space_write_4(iot, ioh, UART_DR, getc(&tp->t_outq));
c = bus_space_read_4(pluartconsiot, pluartconsioh, UART_DR);
bus_space_write_4(pluartconsiot, pluartconsioh, UART_DR, (uint8_t)c);