[PATCH 1/2] powerpc: document the MPIC device tree binding

[Yoder Stuart-B08248]

> +** Optional properties:
> +
> +   - no-reset : The presence of this property indicates that the MPIC
> +                should not be reset during runtime initialization.
> +   - protected-sources : Specifies a list of interrupt sources that are
> + not
> +                         available for use and whose corresponding
> + vectors
> +                         should not be initialized.  A typical use case
> + for
> +                         this property is in AMP systems where multiple
> +                         independent operating systems need to share
> + the MPIC
> +                         without clobbering each other.

Is "protected-sources" really needed for AMP systems to
tell the OSes not to clobber each other?  Won't each
OS be given a device tree with only its interrupt
sources?  ...so you know what you are allowed to touch.

Stuart