That sounds more like a distribution thing, rather than the kernel itself. You can follow through the boot execution order by seeing what /etc/inittab calls. There should be a line that starts with si - look for something like:
# System initialization.
Then you can look at /etc/rc.d/rc.sysinit to see where it mentions F5 and what it does with it.
My guess is that it's probably not going to be as straightforward as you had first hoped!