AM2431: I don't understand the explanation of firewalls in TRM "3.3.2 Interconnect Firewalls"

Tool/software:

The TRM refers to spruim2g.pdf.

TRM section "3.3.2 Interconnect Firewalls" states that "A firewall is not associated with a single target module but with a cloud of target modules."

But I don't understand what that means.

I would like some concrete explanations and examples.

Thank you in advance.