Man pages matching name sd_bus_set_fd in section 3:

sd_bus_set_fd.3.en	debian 11 / libelogind-dev-doc
sd_bus_set_fd.3.en	debian 11 / libsystemd-dev
sd_bus_set_fd.3.en	debian 12 / libelogind-dev-doc
sd_bus_set_fd.3.en	debian 12 / libsystemd-dev