prom_tree_update
extern int prom_tree_update(int (*callback)(void *arg), void *arg);
rv = prom_tree_update(sg_attach_board, hp);
rv = prom_tree_update(sg_detach_board, hp);
(void) prom_tree_update(sg_attach_board, hp);
error = prom_tree_update(sysc_attach_board, &board);
error = prom_tree_update(sysc_detach_board, &board);