Wireshark · Wireshark-dev: [Wireshark-dev] what does the function "proto_register_subtree_array" used for in register of every

["??????????" <237825552@xxxxxx>]

hello,i wanna know what does the function "proto_register_subtree_array" used for in register of every protocol?eg:

in packet-ieee1722.c file:

   /* Register the protocol name and description */

    proto_1722 = proto_register_protocol("IEEE 1722 Protocol", "IEEE1722", "ieee1722");

    /* Required function calls to register the header fields and subtrees used */

    proto_register_field_array(proto_1722, hf, array_length(hf));

    proto_register_subtree_array(ett, array_length(ett));

and what does the ett used for?