serial8250_rx_chars
lsr = serial8250_rx_chars(up, lsr);
status = serial8250_rx_chars(up, status);
EXPORT_SYMBOL_GPL(serial8250_rx_chars);
status = serial8250_rx_chars(up, status);
u16 serial8250_rx_chars(struct uart_8250_port *up, u16 lsr);