struct tty_ldisc n_touch_ldisc = {
    TTY_LDISC_MAGIC,         /* Magic */
    "n_tch",                 /* Name of the line discipline */
    N_TCH,                   /* Line discipline ID number */
    n_touch_open,            /* Open the line discipline */
    n_touch_close,           /* Close the line discipline */
    n_touch_flush_buffer,    /* Flush the line discipline's read
                                buffer */
    n_touch_chars_in_buffer, /* Get the number of processed characters in
                                the line discipline's read buffer */
    n_touch_read,            /* Called when data is requested
                                from user space */
    n_touch_write,           /* Write method */
    n_touch_ioctl,           /* I/O Control commands */
    NULL,                    /* We don't have a set_termios
                                routine */
    n_touch_poll,            /* Poll */
    n_touch_receive_buf,     /* Called by the low-level driver
                                to pass data to user space*/
    n_touch_receive_room,    /* Returns the room left in the line
                                discipline's read buffer */
    n_touch_write_wakeup     /* Called when the low-level device
                                driver is ready to transmit more
                                data */
};

/* ... */

if ((err = tty_register_ldisc(N_TCH, &n_touch_ldisc))) {
    return err;
}