dm: panel: Add a panel uclass

LCD panels can usefully be modelled as their own uclass. They can be probed
(which powers them up ready for use). If they have a backlight, this can be
enabled.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/panel.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2016 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _PANEL_H
+#define _PANEL_H
+
+struct panel_ops {
+	/**
+	 * enable_backlight() - Enable the panel backlight
+	 *
+	 * @dev:	Panel device containing the backlight to enable
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*enable_backlight)(struct udevice *dev);
+};
+
+#define panel_get_ops(dev)	((struct panel_ops *)(dev)->driver->ops)
+
+/**
+ * panel_enable_backlight() - Enable the panel backlight
+ *
+ * @dev:	Panel device containing the backlight to enable
+ * @return 0 if OK, -ve on error
+ */
+int panel_enable_backlight(struct udevice *dev);
+
+#endif