Hello Slava, good morning
In theory you don't need do something about it, when you register a new machine, you will use a activation key, where in the name you can see the org, for example:
1-centosbase6.5 - Base in Org 1
2-centosbase6.5 - Base in Org 2
So if you use 1-centosbase6.5, will register in org 1, if use 2-centosbase6.5, will be in the second.
If you register using username and password, will be according the org admin that you will use to register the machine.
Sure, this in theory, but I believe this will works fine.
Let me know if work for you.