Does this get attached to the `returns` description? I would put some of it in the handler's description since it's part of the overall operation of the handler.

I think it would be more clear to phrase this in terms of the the overall action the kernel is performing instead of what goes into the drivers. Something like: Return a value other than `undefined` to indicate that the driver has handled the action. The value returned may be different from `propertyValue`, in which case that value will be taken as the value actually assigned.

The note about `satProperty` should be in the kernel API's description of `setProperty`, etc., at least. I don't know that we should talk about view drivers more explicitly here than the "value actually assigned" reference. I'd rather see that in the kernel docs where the actions are described and leave the driver docs to talk about the driver's individual responsibilities and expectations.