dt-bindings: phy: imx8mq-usb: add phy tuning properties

Add optional properties for tuning of usb phy.

Signed-off-by: Johannes Zink <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/devicetree/bindings/phy/fsl,imx8mq-usb-phy.yaml

···
     description:
       A phandle to the regulator for USB VBUS.
 
+  fsl,phy-tx-vref-tune-percent:
+    description:
+      Tunes the HS DC level relative to the nominal level
+    minimum: 94
+    maximum: 124
+
+  fsl,phy-tx-rise-tune-percent:
+    description:
+      Adjusts the rise/fall time duration of the HS waveform relative to
+      its nominal value
+    minimum: 97
+    maximum: 103
+
+  fsl,phy-tx-preemp-amp-tune-microamp:
+    description:
+      Adjust amount of current sourced to DPn and DMn after a J-to-K
+      or K-to-J transition. Default is 0 (disabled).
+    minimum: 0
+    maximum: 1800
+
+  fsl,phy-tx-vboost-level-microvolt:
+    description:
+      Adjust the boosted transmit launch pk-pk differential amplitude
+    minimum: 880
+    maximum: 1120
+
+  fsl,phy-comp-dis-tune-percent:
+    description:
+      Adjust the voltage level used to detect a disconnect event at the host
+      relative to the nominal value
+    minimum: 91
+    maximum: 115
+
+  fsl,phy-pcs-tx-deemph-3p5db-attenuation-db:
+    description:
+      Adjust TX de-emphasis attenuation in dB at nominal
+      3.5dB point as per USB specification
+    $ref: /schemas/types.yaml#/definitions/uint32
+    minimum: 0
+    maximum: 36
+
+  fsl,phy-pcs-tx-swing-full-percent:
+    description:
+      Scaling of the voltage defined by fsl,phy-tx-vboost-level-microvolt
+    minimum: 0
+    maximum: 100
+
 required:
   - compatible
   - reg