macctrl_tree = proto_item_add_subtree(ti, ett_macctrl);
proto_tree_add_uint(macctrl_tree, hf_macctrl_opcode, tvb, 0, 2, opcode);
macctrl_tree = proto_item_add_subtree(ti, ett_macctrl);
proto_tree_add_uint(macctrl_tree, hf_macctrl_opcode, tvb, 0, 2, opcode);