[PATCH v4 2/7] dt-bindings: serial: 8250: aspeed: add aspeed,vuart-over-pci bool prop

[Grégoire Layet]

The ASPEED AST2600 has 2 Virtual UARTs accessible over PCI.
The ASPEED AST2600 can be used as a PCI device.
2 Virtual UART can be exposed to the host via this PCI device.
These are 8250-compatible register sets and can be used to have UART
communication between the PCI BMC and the host.

This boolean can be set to specify if a VUART is used over PCI. A VUART
over PCI needs a syscon phandle. The syscon gives a regmap to the SCU,
which is used to set the enable bits of the PCI device.
On the aspeed's chips, the clocks phandle already points at the SCU node.
But deriving the regmap from the clock provider would misuse the clocks
binding. An explicit syscon phandle states the dependency directly.

Signed-off-by: Grégoire Layet <gregoire.layet@xxxxxxxxxxxxx>
---
 .../devicetree/bindings/serial/8250.yaml      | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/8250.yaml b/Documentation/devicetree/bindings/serial/8250.yaml
index 8f22121381fc..2ea8981bba80 100644
--- a/Documentation/devicetree/bindings/serial/8250.yaml
+++ b/Documentation/devicetree/bindings/serial/8250.yaml
@@ -27,6 +27,16 @@ allOf:
             enum:
               - aspeed,ast2500-vuart
               - aspeed,ast2600-vuart
+  - if:
+      required:
+        - aspeed,vuart-over-pci
+    then:
+      required:
+        - syscon
+      properties:
+        compatible:
+          contains:
+            const: aspeed,ast2600-vuart
   - if:
       properties:
         compatible:
@@ -223,6 +233,12 @@ properties:
           - const: uartclk
           - const: reg
 
+  syscon:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Phandle to the SCU syscon, used to enable the VUART over the BMC PCI
+      device. Only applicable to aspeed,ast2600-vuart.
+
   dmas:
     minItems: 1
     maxItems: 4
@@ -316,6 +332,12 @@ properties:
       polarity (IRQ_TYPE_LEVEL_LOW or IRQ_TYPE_LEVEL_HIGH). Only
       applicable to aspeed,ast2500-vuart and aspeed,ast2600-vuart.
 
+  aspeed,vuart-over-pci:
+    type: boolean
+    description:
+      Enable the VUART over the BMC PCI device. Only applicable to
+      aspeed,ast2600-vuart.
+
 required:
   - reg
   - interrupts
-- 
2.54.0