Add '#feature-domain-cells' property description to the scmi node.
This property makes scmi node as feature-domain-controller provider, which
allows consumers to provide scmi node with the device_ids of the devices,
which are using scmi protocols to control clocks/resets/power-domains etc.
The device_ids could be used to set the device permissions for the
Firmware using BASE_SET_DEVICE_PERMISSIONS message (see 4.2.2.10 of [0]).
Device permissions management described in DEN 0056, Section 4.2.2.10 [0].

For SCMI this property is used by Trusted Agent to set the device
permissions for the Non-Trusted Agents.
Trusted and non-trusted Agent terms described in Section 4.1.1 [0].

[0] https://developer.arm.com/documentation/den0056/latest

Signed-off-by: Oleksii Moisieiev <redacted>
---
Changes v1 -> V2:
   - update parameter name, made it xen-specific
   - add xen vendor bindings

Changes V2 -> V3:
   - update parameter name, make it generic
   - update parameter format, add link to controller
   - do not include xen vendor bindings as already upstreamed

Changes V3 -> V4:
   - introduce domain controller provider/consumer device tree bindings
   - making scmi node to act as domain controller provider when the
     device permissions should be configured

Changes V4 -> V5:
   - rename domain-controller to feature-domain-controller
   - feature-domains format fixes

Changes V5 -> V6:
   - formatting fixes
---
 .../bindings/firmware/arm,scmi.yaml           | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
index 1c0388da6721..bb5aa49e88fd 100644
--- a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
+++ b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml

@@ -89,6 +89,16 @@ properties:
       atomic mode of operation, even if requested.
     default: 0
 
+  '#feature-domain-cells':
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Number of cells in a domain controller specifier.
+      Set const to 1 here for nodes providing the device id, needed for
+      the BASE_SET_DEVICE_PERMISSIONS message (see 4.2.2.10 of [0]).
+    const: 1
+
+  feature-domain-controller: true
+
   arm,smc-id:
     $ref: /schemas/types.yaml#/definitions/uint32
     description:

@@ -429,4 +439,22 @@ examples:
         };
     };
 
+  - |
+    firmware {
+        scmi_link: scmi {
+            compatible = "arm,scmi-smc";
+            shmem = <&cpu_scp_lpri0 &cpu_scp_lpri1>;
+            arm,smc-id = <0xc3000001>;
+
+            #address-cells = <1>;
+            #size-cells = <0>;
+            feature-domain-controller;
+            #feature-domain-cells = <1>;
+        };
+    };
+
+    foo@0 {
+      reg = <0x0 0x10>;
+      feature-domains = <&scmi_link 1>;
+    };
 ...

-- 
2.25.1

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