of_tree_walk
if ((match = of_tree_walk(child, fn, ctx)) != NULL)
child = of_tree_walk(&of_root, of_match_by_nodeid, &childid);
child = of_tree_walk(&of_root, of_match_by_parentid, &parentid);
node = of_tree_walk(&of_root, of_match_by_nodeid, &peerid);
node = of_tree_walk(&of_root, of_match_by_nodeid, &nodeid);