Deferred driver probing

Would this correspond at all with the power domains work? In other words, do device manufacturers ensure that these seemingly unrelated devices share a "power domain" which might be usable as a means of triggering probing? Unfortunately it's not clear to me how power domains are created based on discovered hardware so I could be talking complete nonsense.

I ask because I seem to recall that power domains are sometimes independent of the device tree topology and these conglomerate devices seem to be as well. Also it seems kind of pointless to power only half of a "device" that is composed in this way...