Platform support policy proposal

There is a fair amount of confusion about the specific operating system platforms, platform versions, etc. that Chef Software, Inc. supports for its products. This RFC will clarify this by calling out the individual operating systems and their releases as explicitly supported or not.
Since we're already being explicit, it'd be nice to mention which tier they count as (I'm assuming Tier 1?). Or would  ChefDK count as its own tier in the Chef Client matrix?