etcremote

/etc/remote

Older UNIX systems had extensive support for serial ports, and OpenBSD retains this support. It is most commonly used for serial consoles (Chapter 6), as well as configuring network devices with a serial port. The file /etc/remote contains descriptions of a wide variety of serial connections. These commonly used entries are found at the very end.

If you're interested in writing your own serial port configurations, take a look at remote(5).