XML-documentation for a namespace

Would you write xml-doc for a namespace? And if yes, how and where?

I would think, if it is possible, maybe an almost empty file like this:

/// <summary>
/// This namespace contains stuff
/// </summary>
namespace Some.Namespace
{

}

But will that work? Since you... "declare", or at least use the namespace in all the other files as well... and what would happen if you wrote an xml-documentation thing somewhere else on the same namespace? Would one be gone? Or would they be merged somehow?