3GPP 38.300 v19.3.0 — the document's own text
4.7.4.6 Inter node discovery
Taught in 4. What NR actually is, in the shape its own document gives it (TSG RAN — the group that specifies the radio, overview).
Inter node discovery is supported via SSB-based and/or CSI-RS-based measurements. An IAB-node can be configured to transmit and receive off synchronization raster SSB signals to discover neighbouring IAB-nodes. The configuration is not expected to create a conflict between IAB-DU SSB transmission and IAB-MT SSB measurement windows.