fdt_subnode_offset
int fdt_subnode_offset(const void *fdt, int parentoffset, const char *name);
tree_child = fdt_subnode_offset(fdto, tree_node,
nnode = fdt_subnode_offset(fdt, target, name);
overlay = fdt_subnode_offset(fdto, fragment, "__overlay__");
ov_sym = fdt_subnode_offset(fdto, 0, "__symbols__");
root_sym = fdt_subnode_offset(fdt, 0, "__symbols__");
ret = fdt_subnode_offset(fdto, fragment, "__overlay__");
int subNode = fdt_subnode_offset(fdt, node, "interrupt-controller");