Man pages matching name bson_character_and_string_routines in section 3:

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