It's refered to as simply Topping, be it sexually, service or whatever. ( and not with the negative assertions).
I would never define it as purely masochistic topping, simply because when I top, I am not masochistic and always defined myself as primarily sadistic (and quite a few s-types are). I am rarely masochisitic and never was until I met Darcy and discovered the joy of recieving pain.
Topping is completely different from domination/dominance. I find it amazingly freeing and have no problem with topping my partner as it is his desire and his desire - to me - is paramount.
Peace