The devicename for parseclocks connected on serial ports is hardwired to /dev/refclock-X in the ntp daemon. The attached udev rule automatically adds /dev/refclock-X symlinks to all /dev/ttySX devices.
Created attachment 103340 [details] Udev rule to create /dev/reflock-X symlinks
it's up to the user to discover what serial device a valid refclock is connected to ... there is no safe way to do that