/*
* Attach a tty to the tty list.
*
* This should be called ONLY once per real tty (including pty's).
* eg, on the sparc, the keyboard and mouse have struct tty's that are
* distinctly NOT usable as tty's, and thus should not be attached to
* the ttylist. This is why this call is not done from tty_alloc().
*
* Device drivers should attach tty's at a similar time that they are
* allocated, or, for the case of statically allocated struct tty's
* either in the attach or (first) open routine.
*/