rpmsg_sendto
ret = rpmsg_sendto(eptdev->ept, kbuf, len, eptdev->chinfo.dst);
EXPORT_SYMBOL(rpmsg_sendto);
err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
int rpmsg_sendto(struct rpmsg_endpoint *ept, const void *data, int len, u32 dst);