SWI_TTY
register_swi_mp(SWI_TTY, siopoll, NULL,
sc->ith = register_swi_mp(SWI_TTY, bt3c_swi_intr, sc,
unregister_swi(sc->ith, SWI_TTY, -1);
unregister_swi(sc->ith, SWI_TTY, -1);
#define SWI_TTY_PENDING (1 << (SWI_TTY - FIRST_SOFTINT))