We can assign different surface and displacement to different faces.

Setting Up Group

To add a selection of faces to a group:

• Change your selection mode to primitives.
• Select the faces in the Viewport.
• In the Viewport, hit the TAB key and select Group to add the faces to the group. 

Assigning Material To Groups

Add a Material.

If you want to assign both Bxdf and displacement shader, you will need to create a collect vop to collect both surface and displacement. 

Assign your group to the material by setting the Material to either a collect vop (see above) or a Bxdf.

Example