When you enter the 1099-INT for these bonds on the federal return, the second or third screen after you enter the 1099-INT itself, you will see a screen headed "Tell us if any of these uncommon situations apply".
Click the box next to "Our state doesn't tax all this interest".
This will open a pull-down menu; click on Maryland.
When you go to your Maryland return, you will see that this interest is not included in Line 2 on the 502.