Domain Access and mother website arguments
If you have installed the Domain Access module, you will have the Domain Access Views module available. First thing you want to do is enable that module if you haven't already.

Once you've done that, you can use the current domain as a filter:


Under Filter Criteria, add "Domain Access: Domain ID"
"Operator" is one of "Current Domain"


Now the view will only return nodes for the domain that the block/page is loaded from.