In reply to chr_sue:
In reply to usnath:
The reg_model defines the structure of your registers in the DUT. This register model might contain sub_maps as required by the structure in the DUT.
But you cannot have a reg_map outside of your top reg_block (register model).
I created a class that extends from the real reg_model and made it my new reg_model. The other maps are defined inside the new reg_model.