3GPP 24.501 v20.0.0 — the document's own text
8.2.6.41 Non-3GPP path switching information
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The UE may include this IE during the registration procedure for mobility registration update if it requests from the network to keep using the user plane resources of the old non-3GPP access during path switching to the new non-3GPP access.