From: Anton Blanchard <anton@samba.org>

This is an adaptation of the new Open Firmware device tree traversal API from
ppc32, originally written by Benjamin Herrenschmidt.  This patch is against
2.6.0-test3, but should apply ok to the latest 2.5 ameslab tree.

These functions are meant to be SMP-safe alternatives to the current set of
query/traversal routines (find_devices, find_type_devices, et al).