phy: rockchip-dp: should be a child device of the GRF

The displayport-phy is fully enclosed in the general register files (GRF).
Therefore as seen from the device-tree it shouldn't be a separate platform-
device but instead a sub-device of the GRF - using the simply-mfd mechanism.

The driver entered the kernel in the current merge-window, so we can still
adapt the binding without needing a fallback, as the binding hasn't been
released with a full kernel yet.

While the edp phy is fully part of the GRF, it doesn't have any separate
register set there, so doesn't get any register-area assigned.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Yakir Yang <ykk@rock-chips.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
diff --git a/drivers/phy/phy-rockchip-dp.c b/drivers/phy/phy-rockchip-dp.c
index 77e2d02..793ecb6 100644
--- a/drivers/phy/phy-rockchip-dp.c
+++ b/drivers/phy/phy-rockchip-dp.c
@@ -86,6 +86,9 @@
 	if (!np)
 		return -ENODEV;
 
+	if (!dev->parent || !dev->parent->of_node)
+		return -ENODEV;
+
 	dp = devm_kzalloc(dev, sizeof(*dp), GFP_KERNEL);
 	if (IS_ERR(dp))
 		return -ENOMEM;
@@ -104,9 +107,9 @@
 		return ret;
 	}
 
-	dp->grf = syscon_regmap_lookup_by_phandle(np, "rockchip,grf");
+	dp->grf = syscon_node_to_regmap(dev->parent->of_node);
 	if (IS_ERR(dp->grf)) {
-		dev_err(dev, "rk3288-dp needs rockchip,grf property\n");
+		dev_err(dev, "rk3288-dp needs the General Register Files syscon\n");
 		return PTR_ERR(dp->grf);
 	}