dt-bindings: net: dsa: microchip: Update ksz device tree bindings for drive strength

Extend device tree bindings to support drive strength configuration for the
ksz* switches. Introduced properties:
- microchip,hi-drive-strength-microamp: Controls the drive strength for
  high-speed interfaces like GMII/RGMII and more.
- microchip,lo-drive-strength-microamp: Governs the drive strength for
  low-speed interfaces such as LEDs, PME_N, and others.
- microchip,io-drive-strength-microamp: Controls the drive strength for
  for undocumented Pads on KSZ88xx variants.
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/microchip,ksz.yaml

@@ -49,6 +49,26 @@ properties:
       Set if the output SYNCLKO clock should be disabled. Do not mix with
       microchip,synclko-125.
 
+  microchip,io-drive-strength-microamp:
+    description:
+      IO Pad Drive Strength
+    enum: [8000, 16000]
+    default: 16000
+
+  microchip,hi-drive-strength-microamp:
+    description:
+      High Speed Drive Strength. Controls drive strength of GMII / RGMII /
+      MII / RMII (except TX_CLK/REFCLKI, COL and CRS) and CLKO_25_125 lines.
+    enum: [2000, 4000, 8000, 12000, 16000, 20000, 24000, 28000]
+    default: 24000
+
+  microchip,lo-drive-strength-microamp:
+    description:
+      Low Speed Drive Strength. Controls drive strength of TX_CLK / REFCLKI,
+      COL, CRS, LEDs, PME_N, NTRP_N, SDO and SDI/SDA/MDIO lines.
+    enum: [2000, 4000, 8000, 12000, 16000, 20000, 24000, 28000]
+    default: 8000
+
   interrupts:
     maxItems: 1