This is MAKEDEV, which knows how to create device nodes under /dev.
MAKEDEV is largely obsoleted by udev on modern systems.
MAKEDEV itself has no direct knowledge of the device nodes which a system
supports, but reads this information from its configuration files.
The intent is to mirror the contents of
devices.txt file as
closely as possible.
The major version is 3 to distinguish between this implemenation and the shell
script 2.5.2 which we previously used.