drivers/net/phy: add fixed-phy / fixed-link support

This patch adds support for having a "fixed-link" to some other MAC
(like some embedded switch-device).

For this purpose we introduce a new phy-driver, called "Fixed PHY".

Fixed PHY works only with CONFIG_DM_ETH enabled, since the fixed-link is
described with a subnode below ethernet interface.

Most ethernet drivers (unfortunately not all are following same scheme
for searching/attaching phys) are calling "phy_connect(...)" for getting
a phy-device.
At this point we link in, we search here for a subnode called "fixed-
link", once found we start phy_device_create(...) with the special phy-
id PHY_FIXED_ID (0xa5a55a5a).

During init the "Fixed PHY" driver has registered with this id and now
gets probed, during probe we get all the details about fixed-link out of
dts, later on the phy reports this values.

Signed-off-by: Hannes Schmelzer <hannes.schmelzer@br-automation.com>

Signed-off-by: Hannes Schmelzer <oe5hpm@oevsv.at>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>
diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 8db6574..8bacd99 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -515,7 +515,9 @@
 #ifdef CONFIG_PHY_MSCC
 	phy_mscc_init();
 #endif
-
+#ifdef CONFIG_PHY_FIXED
+	phy_fixed_init();
+#endif
 	return 0;
 }
 
@@ -854,9 +856,24 @@
 		struct eth_device *dev, phy_interface_t interface)
 #endif
 {
-	struct phy_device *phydev;
+	struct phy_device *phydev = NULL;
+#ifdef CONFIG_PHY_FIXED
+	int sn;
+	const char *name;
+	sn = fdt_first_subnode(gd->fdt_blob, dev->of_offset);
+	while (sn > 0) {
+		name = fdt_get_name(gd->fdt_blob, sn, NULL);
+		if (name != NULL && strcmp(name, "fixed-link") == 0) {
+			phydev = phy_device_create(bus,
+						   sn, PHY_FIXED_ID, interface);
+			break;
+		}
+		sn = fdt_next_subnode(gd->fdt_blob, sn);
+	}
+#endif
+	if (phydev == NULL)
+		phydev = phy_find_by_mask(bus, 1 << addr, interface);
 
-	phydev = phy_find_by_mask(bus, 1 << addr, interface);
 	if (phydev)
 		phy_connect_dev(phydev, dev);
 	else