On Thu, Sep 28, 2017 at 3:11 PM, Sudeep Holla [off-list ref] wrote:

+
+The SCMI is intended to allow agents such as OSPM to manage various functions
+that are provided by the hardware platform it is running on, including power
+and performance functions.
+
+This binding is intended to define the interface the firmware implementing
+the SCMI as described in ARM document number ARM DUI 0922B ("ARM System Control
+and Management Interface Platform Design Document")[0] provide for OSPM in
+the device tree.
+
+Required properties:
+
+The scmi node with the following properties shall be under the /firmware/ node.
+
+- compatible : shall be "arm,scmi"
+- mboxes: List of phandle and mailbox channel specifiers. It should contain
+         exactly one or two mailboxes, one for transmitting messages("tx")
+         and another optional for receiving the notifications("rx") if
+         supported.
+- mbox-names: shall be "tx" or "rx"

The example below does not have the mbox-names property. If you require
exactly two mailboxes, why do you need the names anyway?

However, your example does have a #addresss-cells/#size-cells
property that are not documented here. Please add them here as either
optional or required, and describe what the permitted values are and
how the address is interpreted.

+- shmem : List of phandle pointing to the shared memory(SHM) area as per
+         generic mailbox client binding.
+
+See Documentation/devicetree/bindings/mailbox/mailbox.txt for more details
+about the generic mailbox controller and client driver bindings.
+
+The mailbox is the only permitted method of calling the SCMI firmware.
+Mailbox doorbell is used as a mechanism to alert the presence of a
+messages and/or notification.

This looks odd: why not make the message itself part of the mailbox
protocol here, and leave the shmem as a implementation detail of the
mailbox driver?

+Each protocol supported shall have a sub-node with corresponding compatible
+as described in the following sections. If the platform supports dedicated
+communication channel for a particular protocol, the 3 properties namely:
+mboxes, mbox-names and shmem shall be present in the sub-node corresponding
+to that protocol.
+
+Clock/Performance bindings for the clocks/OPPs based on SCMI Message Protocol
+------------------------------------------------------------
+
+This binding uses the common clock binding[1].
+
+Required properties:
+- #clock-cells : Should be 1. Contains the Clock ID value used by SCMI commands.
+

How does the OS identify the fact that a subnode uses the clock binding?
Do you need to look for the #clock-cells property, or is this based on the
unit address?

          Arnd