Add core SCMI Notifications dispatch and delivery support logic which is
able, at first, to dispatch well-known received events from the RX ISR to
the dedicated deferred worker, and then, from there, to final deliver the
events to the registered users' callbacks.

Dispatch and delivery is just added here, still not enabled.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
 drivers/firmware/arm_scmi/notify.c | 354 ++++++++++++++++++++++++++++-
 drivers/firmware/arm_scmi/notify.h |  10 +
 2 files changed, 362 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_scmi/notify.c b/drivers/firmware/arm_scmi/notify.c
index 7cf61dbe2a8e..d582f71fde5b 100644
--- a/drivers/firmware/arm_scmi/notify.c
+++ b/drivers/firmware/arm_scmi/notify.c

@@ -1085,6 +1422,12 @@ int scmi_notification_init(struct scmi_handle *handle)
 	ni->gid = gid;
 	ni->handle = handle;
 
+	ni->notify_wq = alloc_workqueue("scmi_notify",
+					WQ_UNBOUND | WQ_FREEZABLE | WQ_SYSFS,
+					0);