Enhance Power Interface for Soft Power Off and Inject NMI

This blue print proposes to enhance the current power interface to support soft power off and diagnostic interrupt (NMI [1]).

Both soft reboot and diagnostic interrupt (NMI) are supported by ipmitool.
$ man ipimtool
....
 power

        Performs a chassis control command to view and change the power state.

        diag

               Pulse a diagnostic interrupt (NMI) directly to the processor(s).

        soft

               Initiate a soft-shutdown of OS via ACPI. This can be
               done in a number of ways, commonly by simulating an
               overtemperture or by simulating a power button press.
               It is necessary for there to be Operating System support
               for ACPI and some sort of daemon watching for events for
               this soft power to work.
....

[1] http://en.wikipedia.org/wiki/Non-maskable_interrupt

- Nov 9th, 2015, Naohirot:
Overall idea can be found in the following presentation slides P.40 - P.54.

"Ironic Towards Truly Open and Reliable, Eventually for Mission Critical"
 http://www.slideshare.net/naohirot/ironic-towards-truly-open-and-reliable-eventually-for-mission-critical
 https://www.youtube.com/watch?v=MpSqDA3jo0I