[dt] Add basic concept of a devicetree bus

Add a basic model for devices instantiated by parsing the system
flattened device tree, with drivers matched via the "compatible"
property for any non-root node.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/device.h

@@ -69,6 +69,9 @@ struct device_description {
 /** USB bus type */
 #define BUS_TYPE_USB 10
 
+/** Devicetree bus type */
+#define BUS_TYPE_DT 11
+
 /** A hardware device */
 struct device {
 	/** Name */

src/include/ipxe/devtree.h

@@ -0,0 +1,76 @@
+#ifndef _IPXE_DEVTREE_H
+#define _IPXE_DEVTREE_H
+
+/** @file
+ *
+ * Devicetree bus
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <ipxe/device.h>
+
+/** A devicetree device */
+struct dt_device {
+	/** Generic device */
+	struct device dev;
+	/** Device path */
+	const char *path;
+	/** Driver for this device */
+	struct dt_driver *driver;
+	/** Driver-private data */
+	void *priv;
+};
+
+/** A devicetree driver */
+struct dt_driver {
+	/** Driver name */
+	const char *name;
+	/** Compatible programming model identifiers */
+	const char **ids;
+	/** Number of compatible programming model identifiers */
+	unsigned int id_count;
+	/**
+	 * Probe device
+	 *
+	 * @v dt		Devicetree device
+	 * @v offset		Starting node offset
+	 * @ret rc		Return status code
+	 */
+	int ( * probe ) ( struct dt_device *dt, unsigned int offset );
+	/**
+	 * Remove device
+	 *
+	 * @v dt		Devicetree device
+	 */
+	void ( * remove ) ( struct dt_device *dt );
+};
+
+/** Devicetree driver table */
+#define DT_DRIVERS __table ( struct dt_driver, "dt_drivers" )
+
+/** Declare a devicetree driver */
+#define __dt_driver __table_entry ( DT_DRIVERS, 01 )
+
+/**
+ * Set devicetree driver-private data
+ *
+ * @v dt		Devicetree device
+ * @v priv		Private data
+ */
+static inline void dt_set_drvdata ( struct dt_device *dt, void *priv ) {
+	dt->priv = priv;
+}
+
+/**
+ * Get devicetree driver-private data
+ *
+ * @v dt		Devicetree device
+ * @ret priv		Private data
+ */
+static inline void * dt_get_drvdata ( struct dt_device *dt ) {
+	return dt->priv;
+}
+
+#endif /* _IPXE_DEVTREE_H */

src/include/ipxe/errfile.h

@@ -231,6 +231,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_aqc1xx		     ( ERRFILE_DRIVER | 0x00d70000 )
 #define ERRFILE_atl_hw		     ( ERRFILE_DRIVER | 0x00d80000 )
 #define ERRFILE_atl2_hw		     ( ERRFILE_DRIVER | 0x00d90000 )
+#define ERRFILE_devtree		     ( ERRFILE_DRIVER | 0x00da0000 )
 
 #define ERRFILE_aoe			( ERRFILE_NET | 0x00000000 )
 #define ERRFILE_arp			( ERRFILE_NET | 0x00010000 )