Players can add a small smithy building to their garrison.  Currently, Blizzard has referred to this as the Blacksmithing Foundry.

The Foundry can be upgraded to level 3.

Followers with the blacksmithing profession can go out in the world to collect blacksmithing mats and find new blacksmithing recipes.

Because there is also a mine in the Garrison, it is believed that it will allow collecting of the actual bars instead of ore.