Steve is really reluctant at first and doesn't want to admit to his feelings, but tony and bruce teach him it's ok to be submissive. It's a pretty slow build and a long fic.
Random details i can remember are that
-tony and bruce call steve pup or puppy
-steve is uncomfortable subbing naked at first so he wears bicycle shorts,
-towards the end steve gets pissed off at tony for coddling and domming him during missions, after tony had promised he would respect steve's authority. Steve then says eff this basically and takes off on a motorcycle journey to get his head clear. He's sad and lonely while he's away and eventually tony apologizes enough and steve goes home.
I'm pretty sure it was on Ao3 but for the life of me i can't remember the title or find it.