dt-bindings: net: thead,th1520-gmac: Describe APB interface clock

Besides ones for GMAC core and peripheral registers, the TH1520 GMAC
requires one more clock for configuring APB glue registers. Describe
it in the binding.

Fixes: f920ce0 ("dt-bindings: net: Add T-HEAD dwmac support")
Signed-off-by: Yao Zi <ziyao@disroot.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Drew Fustini <fustini@kernel.org>
Link: https://patch.msgid.link/20250808093655.48074-3-ziyao@disroot.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: ziyao233

Documentation/devicetree/bindings/net/thead,th1520-gmac.yaml

@@ -62,11 +62,13 @@ properties:
     items:
       - description: GMAC main clock
       - description: Peripheral registers interface clock
+      - description: APB glue registers interface clock
 
   clock-names:
     items:
       - const: stmmaceth
       - const: pclk
+      - const: apb
 
   interrupts:
     items:
@@ -88,8 +90,8 @@ examples:
         compatible = "thead,th1520-gmac", "snps,dwmac-3.70a";
         reg = <0xe7070000 0x2000>, <0xec003000 0x1000>;
         reg-names = "dwmac", "apb";
-        clocks = <&clk 1>, <&clk 2>;
-        clock-names = "stmmaceth", "pclk";
+        clocks = <&clk 1>, <&clk 2>, <&clk 3>;
+        clock-names = "stmmaceth", "pclk", "apb";
         interrupts = <66>;
         interrupt-names = "macirq";
         phy-mode = "rgmii-id";