Definition:


{ &hf_mongo_msg_sections_section,
    { "Section", *"mongo.msg.sections.section",*
    *FT_NONE,* BASE_NONE, NULL, 0x0,
    NULL, HFILL }
},

Add to tree:


ti = proto_tree_add_item(
    tree,
    *hf_mongo_msg_sections_section,*
    tvb, offset, 1 + section_len,
    ENC_NA
);

*section_tree* = proto_item_add_subtree(ti, ett_mongo_section);