Identify your IPI mailbox channel. IPI naming follows the pattern
ipi_<src>_to_ipi_<dst> or
ipi_<src>_nobuf_to_ipi_<dst>_nobuf, depending on the SoC.
Check the SDT for available mailbox child nodes.
rpmsg-relation:
compatible: openamp,rpmsg-v1
relation0:
remote: RPU_Zephyr
carveouts: [ vdev0vring0@9860000, vdev0vring1@9864000, vdev0buffer@9868000 ]
mbox: ipi_1_nobuf_to_ipi_2_nobuf # APU→RPU IPI