v4.19.13 snapshot.
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+What: /sys/bus/mdio_bus/devices/.../phy_id
+Date: November 2012
+KernelVersion: 3.8
+Contact: netdev@vger.kernel.org
+Description:
+ This attribute contains the 32-bit PHY Identifier as reported
+ by the device during bus enumeration, encoded in hexadecimal.
+ This ID is used to match the device with the appropriate
+ driver.
+
+What: /sys/bus/mdio_bus/devices/.../phy_interface
+Date: February 2014
+KernelVersion: 3.15
+Contact: netdev@vger.kernel.org
+Description:
+ This attribute contains the PHY interface as configured by the
+ Ethernet driver during bus enumeration, encoded in string.
+ This interface mode is used to configure the Ethernet MAC with the
+ appropriate mode for its data lines to the PHY hardware.
+
+What: /sys/bus/mdio_bus/devices/.../phy_has_fixups
+Date: February 2014
+KernelVersion: 3.15
+Contact: netdev@vger.kernel.org
+Description:
+ This attribute contains the boolean value whether a given PHY
+ device has had any "fixup" workaround running on it, encoded as
+ a boolean. This information is provided to help troubleshooting
+ PHY configurations.