3GPP 23.501 v20.2.0 — the document's own text
6.1 General
Taught in 4. What each network function does (The 5G system architecture, in depth), 2. Who does what in the core (The 5G system architecture, overview), 2. The pieces a 5G core is made of (The 5G system architecture, quick start).
Clause 6 provides the functional description of the Network Functions and network entities and the principles for Network Function and Network Function Service discovery and selection.
NG-RAN functions and entities are described in TS 38.300 [27] and TS 38.401 [42].
Security functions and entities are described in TS 33.501 [29] and TS 33.535 [124].
5G Media streaming functions are described in TS 26.501 [135].