Fiqh of Nikah of A Male Slave & Free Woman

What is Fiqh of Nikah of Male Slave owned by someone else to free woman? I mean a male slave who is owned by someone else and marries a free woman who is not related to her master nor is her mistress. What is rule related to the children born from such marriage? I know the marriage of freeing man to someone's slave girl and the children born of it are owned by masters.