GPIO - marking individual pins (not) available in device tree

[Mitch Bradley]

> Right. I had a similar discussion about this the other day with Anton (I
> think he forwarded it here but I wasn't subscribed at that point..). The
> current ideology for device trees is to get rid of device_type for new
> trees that aren't OF-based. I think it's relevant to give nodes fancy
> names (i.e. not "timer" or even "ethernet") since the name property is
> entirely descriptive in nature. I also think it's relevant that 
> device_type
> still exists because since the name is totally irrelevant except from a
> user-friendliness point of view, marking a device as a generic type is
> quite important (device_type = serial, ethernet, rtc, keyboard) where
> compatible properties are usually wildly over-specific.

I don't use device_type much, if at all, anymore.  Generic name + compatible
just works better than device_type + specific name.  When I write code that
has to find a node that is suitable for a given purpose, I look for the 
existence
of suitable methods and perhaps other properties.  I was just too hard to
keep the list of device_type values properly synchronized with all the 
possible
things that you might want to infer from that set of names.

device_type is one of those things that seemed like a good idea at the time,
but didn't work out as well as I had hoped.