Does anyone know if the dawnguard armor gets benefit of the steel smithing perk?

There is one way to find out. Try it.

My char with 30 smithing and steel smithing perk, got the light armor version to superior.

Not sure about heavy armor though.

I got it to Legendary so I assume so.

I would think it would work for both.

I got it to Flawless with 100 smithing on my character. Took Steel, Dwarven, Orcish, Ebony, Daedric, and Dragon.

But I did get it to Legendary on another character. I suspect it may be the Advanced perk on the light side.