netdev/phy: Add driver for Broadcom BCM87XX 10G Ethernet PHYs

Add a driver for BCM8706 and BCM8727 devices.  These are a 10Gig PHYs
which use MII_ADDR_C45 addressing.  They are always 10G full duplex, so
there is no autonegotiation.  All we do is report link state and send
interrupts when it changes.

If the PHY has a device tree of_node associated with it, the
"broadcom,c45-reg-init" property is used to supply register
initialization values when config_init() is called.

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/broadcom-bcm87xx.txt

@@ -0,0 +1,29 @@
+The Broadcom BCM87XX devices are a family of 10G Ethernet PHYs.  They
+have these bindings in addition to the standard PHY bindings.
+
+Compatible: Should contain "broadcom,bcm8706" or "broadcom,bcm8727" and
+            "ethernet-phy-ieee802.3-c45"
+
+Optional Properties:
+
+- broadcom,c45-reg-init : one of more sets of 4 cells.  The first cell
+  is the MDIO Manageable Device (MMD) address, the second a register
+  address within the MMD, the third cell contains a mask to be ANDed
+  with the existing register value, and the fourth cell is ORed with
+  he result to yield the new register value.  If the third cell has a
+  value of zero, no read of the existing value is performed.
+
+Example:
+
+	ethernet-phy@5 {
+		reg = <5>;
+		compatible = "broadcom,bcm8706", "ethernet-phy-ieee802.3-c45";
+		interrupt-parent = <&gpio>;
+		interrupts = <12 8>; /* Pin 12, active low */
+		/*
+		 * Set PMD Digital Control Register for
+		 * GPIO[1] Tx/Rx
+		 * GPIO[0] R64 Sync Acquired
+		 */
+		broadcom,c45-reg-init = <1 0xc808 0xff8f 0x70>;
+	};