[PATCH 2/2] dt-bindings: riscv: Add Xuantie C906/C908/C910/C920 compatibles

[Shengyu Qu]

Can't we just replace all existing dts' thead to xuantie? So we can 
remove thead here.

> Add equivalent compatibles using the newly defined xuantie vendor
> prefix. Keep the existing thead compatibles to preserve compatibility
> with existing device trees.
> 
> Cc: Conor Dooley <conor.dooley at microchip.com>
> Cc: Rob Herring <robh+dt at kernel.org>
> Cc: devicetree <devicetree at vger.kernel.org>
> Signed-off-by: GUO Ren (XuanTie) <guoren at kernel.org>
> ---
>   Documentation/devicetree/bindings/riscv/cpus.yaml | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> index 5feeb2203050..5aba1e8ed195 100644
> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> @@ -67,6 +67,10 @@ properties:
>                 - thead,c908
>                 - thead,c910
>                 - thead,c920
> +              - xuantie,c906
> +              - xuantie,c908
> +              - xuantie,c910
> +              - xuantie,c920
>             - const: riscv
>         - items:
>             - enum: