Merge branch 'pm-doc'

subsystem-level callbacks.  Specifically, if a device's pm_domain pointer is

not NULL, the ->suspend() callback from the object pointed to by it will be

executed instead of its subsystem's (e.g. bus type's) ->suspend() callback and

anlogously for all of the remaining callbacks.  In other words, power management

domain callbacks, if defined for the given device, always take precedence over

the callbacks provided by the device's subsystem (e.g. bus type).

analogously for all of the remaining callbacks.  In other words, power

management domain callbacks, if defined for the given device, always take

precedence over the callbacks provided by the device's subsystem (e.g. bus

type).

The support for device power management domains is only relevant to platforms

needing to use the same device driver power management callbacks in many

Device Low Power (suspend) States

---------------------------------

Device low-power states aren't standard.  One device might only handle

"on" and "off, while another might support a dozen different versions of

"on" and "off", while another might support a dozen different versions of

"on" (how many engines are active?), plus a state that gets back to "on"

faster than from a full "off".