net: ethernet: nb8800: support fixed-link DT node

Under some circumstances, e.g. when connecting to a switch, the ethernet
port will not be connected to a PHY. In that case a "fixed-link" DT node
can be used to replace it.

https://stackoverflow.com/questions/31046172/device-tree-for-phy-less-connection-to-a-dsa-switch

This patch adds support for the "fixed-link" node to the nb8800 driver.
Signed-off-by: Sebastian Frias <sf84@laposte.net>
Acked-by: Mans Rullgard <mans@mansr.com>
Cc: Mason <slash.tmp@free.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/aurora/nb8800.c

@@ -1460,7 +1460,19 @@ static int nb8800_probe(struct platform_device *pdev)
 		goto err_disable_clk;
 	}
 
-	priv->phy_node = of_parse_phandle(pdev->dev.of_node, "phy-handle", 0);
+	if (of_phy_is_fixed_link(pdev->dev.of_node)) {
+		ret = of_phy_register_fixed_link(pdev->dev.of_node);
+		if (ret < 0) {
+			dev_err(&pdev->dev, "bad fixed-link spec\n");
+			goto err_free_bus;
+		}
+		priv->phy_node = of_node_get(pdev->dev.of_node);
+	}
+
+	if (!priv->phy_node)
+		priv->phy_node = of_parse_phandle(pdev->dev.of_node,
+						  "phy-handle", 0);
+
 	if (!priv->phy_node) {
 		dev_err(&pdev->dev, "no PHY specified\n");
 		ret = -ENODEV;