The category of smooth Banach manifolds has a full and faithful functor into the category of diffeological spaces. In terms of Chen smooth spaces this was observed in (Hain), a discussion for genuine diffeological spaces is in the textbook (Iglesias-Zemmour, exercise 72).
For general references see at infinite-dimensional manifold.
The embedding into the category of diffeological spaces is discussed in
More on this is in exercise 72 of