For starters, specifications are available free on the Internet. Because 26 individual specifications exist, they should be grouped into categories. Grouping titles helps. Architectural framework documents obviously pertain to architecture. Call flows are a type of signal flow.
Protocols are the rules governing communication between the blocks of an architecture.
Fine-tuning with additional categories can always be done later. Categorizing other documents requires skimming architecture documents. What you are looking for is a definition of the main architectural components of PacketCable, and their relationship to each other. The PacketCable technical reports covering architectural framework are good sources. One PacketCable document exists each for PSTN gateway protocol and call management server.