Documentation for partitioned indexes?

We appear to have a fair amount of support now for operations like
constructing a partitioned index piecemeal, e.g. adding indexes
to the partitions one at a time and then attaching them to a
parent partitioned index, with the parent ultimately transitioning
from "not valid" to "valid" once all the pieces are attached.

However, I cannot find any coherent documentation explaining how
to do this (or why you'd want to).  Am I just looking in the wrong
places?

			regards, tom lane