What type of wiring should bedroom overhead lighting have?
I think you may be referring to the addition of item C to section 404.2 in article 404 of the National Electrical Code (NEC). Which states...

National Electrical Code 2011
ARTICLE 404 Switches
404.2 Switch Connections.
(C) Switches Controlling Lighting Loads. Where switches control lighting loads supplied by a grounded general purpose branch circuit, a grounded circuit conductor shall be provided at the switch location.
Exception: The grounded circuit conductor shall be permitted to be omitted from the switch enclosure where either of the conditions in (1) or (2) apply:
(1) Conductors for switches controlling lighting loads enter the device box through a raceway.
(2) Cable assemblies for switches controlling lighting enter the box through a framing cavity that is open at the top or bottom on the same floor level, or through a wall, floor, or ceiling that is unfinished on one side.

The intention of this code change is to provide a grounded (neutral) conductor in switch boxes, so &quot;smart&quot; devices can make use of it.