I would change this to "it's okay to call phy_drivers_unregister from a
different thread than the one in which phy_drivers_register was called".

This got me thinking about 'threads'. For register and unregister, we
are talking abut the kernel modules module_init() and module_exit()
function. module_init() can be called before user space is even
started, but it could also be called by insmod. module_exit() could be
called by rmmod, but it could also be the kernel, after user space has
gone away on shutdown. We are always in a context which can block, but
i never really think of this being threads. You can start a kernel
thread, and have some data structure exclusively used by that kernel
thread, but that is pretty unusual.

So i would probably turn this commenting around. Only comment like
this in the special case that a kernel thread exists, and it is
expected to have exclusive access.

	 Andrew