3GPP 23.501 v20.2.0 — the document's own text

8.2.3.1 The Control Plane Protocol Stack for the service based interface

Taught in 8. What actually travels on the wire (The 5G system architecture, in depth), 3. How one function calls another (The 5G system architecture, overview).

The control plane protocol(s) for the service-based interfaces listed in clause 4.2.6 is defined in the TS 29.500 [49]