The config_intrhook mechanism allows a driver to stall the boot process until device(s) required for booting are available, by not allowing system inits to proceed until all intrhook functions have been unregistered. Virtually all existing code simply unregisters from within the hook function when it gets called.
This new function makes that common usage more convenient. Instead of allocating and filling in a struct, passing it to a function that might (in theory) fail, and checking the return code, now a driver can simply call this cannot-fail routine, passing just the intrhook function to call and its arg.