Some SCMI transport could need to perform some transport specific setup
before they can be used by the SCMI core transport layer: typically this
early setup consists in registering with some other kernel subsystem.

Add the optional capability for a transport to provide a couple of .init
and .exit functions that are assured to be called early during the SCMI
core initialization phase, well before the SCMI core probing step.

[ Peter: Adapted RFC patch by Cristian for submission to upstream. ]
Signed-off-by: Peter Hilber <redacted>
[ Cristian: Fixed scmi_transports_exit point of invocation ]
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
v4 --> V5
- removed useless pr_debug
- moved scmi_transport_exit() invocation
---
 drivers/firmware/arm_scmi/common.h |  8 +++++
 drivers/firmware/arm_scmi/driver.c | 56 ++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+)

diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 7c2b9fd7e929..6bb734e0e3ac 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h

@@ -321,6 +321,12 @@ struct scmi_device *scmi_child_dev_find(struct device *parent,
 /**
  * struct scmi_desc - Description of SoC integration
  *
+ * @init: An optional function that a transport can provide to initialize some
+ *	  transport-specific setup during SCMI core initialization, so ahead of
+ *	  SCMI core probing.
+ * @exit: An optional function that a transport can provide to de-initialize
+ *	  some transport-specific setup during SCMI core de-initialization, so
+ *	  after SCMI core removal.
  * @ops: Pointer to the transport specific ops structure
  * @max_rx_timeout_ms: Timeout for communication with SoC (in Milliseconds)
  * @max_msg: Maximum number of messages that can be pending

@@ -328,6 +334,8 @@ struct scmi_device *scmi_child_dev_find(struct device *parent,
  * @max_msg_size: Maximum size of data per message that can be handled.
  */
 struct scmi_desc {
+	int (*init)(void);
+	void (*exit)(void);