It is not a driver, it is a subsystem. There is no read, write,
ioctl
Drivers register with it but keylock is not a driver.
Sounds a lot like src/sys/dev/sysmon - a subsystem I'm rather
familiar with.
Can you add a src/sys/dev/keylock directory for your subsystem?
I think this does not warrant a whole subdirectory, it's a single
file. And it is not device driver, so I hardly see why it should be
under dev/.
It looks very similar in functionality to what sysmon(4) does
(normalise data from drivers, and export to userland or other kernel
parts). It's also somewhat similar to ld(4), or the audio(4)
subsystem.
If you're confident it won't grow beyond a single file, it doesn't
need its
own subdirectory. But I think it should be in dev/, in the same place
as other similar subsystems, for consistency.