Hi Christian,
I've looked but can't find any graphical representations but couldn't find any so I'll do my best with good ole text. :)
1. Think of the sub-interface as it's own interface. So when you see "interface ATM0/0.1" for example, you know that it's sub-interface number 1 under the MAIN interface ATM0/0.
2. Considering point #1 your PVC / IP address QOS will be specific to what is under ".1". For instance let's say we have two PVCs under ATM0/0 (on sub-interfaces 1 & 2).
3640-12(config)#int atm0/0.1
3640-12(config-subif)#ip address 123.123.123.1 255.255.255.252
3640-12(config-subif)#pvc 1/123
3640-12(config)#int atm0/0.2
3640-12(config-subif)#ip address 12.12.12.1 255.255.255.252
3640-12(config-subif)#pvc 12/12
The IP addresses and PVCs are specific to the sub-interface sub-sets so all the rules apply (split horizon etc). There are two totally separate data paths.
Some documetns you may find useful are here:
"ATM PVC, SVC, Soft-PVC, and PVP Frequently Asked Questions"
http://www.cisco.com/en/US/tech/tk39/tk48/technologies_q_and_a_item09186a008011a901.shtml#qa1
"Configuring ATM"
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/wan_c/wcatm.htm
Hope this helps...
-Tim
