Unfortunately, there is no such functionality available out of the box. You could implement this by adding custom HttpModule to load the home page corresponding to each domain. Next, you need to modify the navigational controls to start from the domain’s root page. Also, if you are going to use shared content, News or Blogs that should be specific to each domain, you'll have to add a provider for each domain and specify different application name for each provider. Then permissions can be set per provider.
We have already tried this approach for a customer and I must say it is not very practical and straightforward. Since there have been quite a lot of requests for such scenarios, we are currently considering providing this functionally out of the box but I can’t promise that it will make it for v3.2.
However, if you decide to give it a try, I can send you more detailed instructions and a sample project. Note that this approach may not be fully compatible with the one that we will provide later.
the Telerik team