Man pages matching name bson_iter_init_from_data_at_offset in section 3:

bson_iter_init_from_data_at_offset.3.en	debian 10 / libbson-doc
bson_iter_init_from_data_at_offset.3.en	debian 11 / libbson-doc
bson_iter_init_from_data_at_offset.3.en	debian 12 / libbson-doc