serial8250_em485_stop_tx
void serial8250_em485_stop_tx(struct uart_8250_port *p, bool toggle_ier);
up->rs485_stop_tx = serial8250_em485_stop_tx;
up->rs485_stop_tx = serial8250_em485_stop_tx;
up.rs485_stop_tx = serial8250_em485_stop_tx;
serial8250_em485_stop_tx(up, true);
EXPORT_SYMBOL_GPL(serial8250_em485_stop_tx);