BTNXPUART_SERDEV_OPEN
set_bit(BTNXPUART_SERDEV_OPEN, &nxpdev->tx_state);
clear_bit(BTNXPUART_SERDEV_OPEN, &nxpdev->tx_state);
!test_bit(BTNXPUART_SERDEV_OPEN, &nxpdev->tx_state))