Man pages matching name keyctl_set_reqkey_keyring in section 3:

keyctl_set_reqkey_keyring.3.en	debian 10 / libkeyutils-dev
keyctl_set_reqkey_keyring.3.en	debian 11 / libkeyutils-dev
keyctl_set_reqkey_keyring.3.en	debian 12 / libkeyutils-dev