Man pages matching name bson_json_reader_new_from_file in section 3:

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