Ability to have multiple private portals to the same product, but have portal users only see ideas submitted in that portal Merged

I have a product where we implement a lot of customer idéas.
For some customers I need to set up a idea portal where we only handle the needs from that customer.

I'd like to set up two portals one customer on each but where all ideas goes to the same product. I don't want the customers to see each others ideas. But at the same time I want all ideas in the same product.

I can set up two different portals and use the domains to control who get access to each portal. But when in the portal (as a customer) I see all posted Ideas from both portals.