net: phy: Document phydev::dev_flags bits allocation

Document the phydev::dev_flags bit allocation to allow bits 15:0 to
define PHY driver specific behavior, bits 23:16 to be reserved for now,
and bits 31:24 to hold generic PHY driver flags.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20210526184617.3105012-1-f.fainelli@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/phy.h

@@ -496,6 +496,11 @@ struct macsec_ops;
  * @mac_managed_pm: Set true if MAC driver takes of suspending/resuming PHY
  * @state: State of the PHY for management purposes
  * @dev_flags: Device-specific flags used by the PHY driver.
+ *		Bits [15:0] are free to use by the PHY driver to communicate
+ *			    driver specific behavior.
+ *		Bits [23:16] are currently reserved for future use.
+ *		Bits [31:24] are reserved for defining generic
+ *			     PHY driver behavior.
  * @irq: IRQ number of the PHY's interrupt (-1 if none)
  * @phy_timer: The timer for handling the state machine
  * @phylink: Pointer to phylink instance for this PHY