3GPP 38.300 v19.3.0 — the document's own text

6.2 MAC Sublayer

Taught in 5. The radio protocol stack, sublayer by sublayer (TSG RAN — the group that specifies the radio, in depth), 2. The six working groups and the line between them (TSG RAN — the group that specifies the radio, overview), 5. The layers a packet falls through, and the three states a device sits in (TSG RAN — the group that specifies the radio, overview).