ttycreate from FreeBSD equivalent

[jon]

Hello, I'm in the process of adapting a driver from freebsd to
openbsd. I was wondering what I should use in place of a call like
ttycreate(tmptty, TS_CALLOUT, "N%r", i);

any hints appreciated, tmptty is a struct tty from /sys/kern/tty.c
(openbsd)