device: added register_class_devname() API

this allows drivers to register generic device names for a device
class, with automatic class instance handling

src/drivers/device/device.h

@@ -396,6 +396,25 @@ protected:
 	 */
 	virtual int	close_last(struct file *filp);
 
+        /**
+	 * Register a class device name, automatically adding device
+	 * class instance suffix if need be.
+	 *
+	 * @param class_devname   Device class name
+	 * @return class_instamce Class instance created, or -errno on failure
+	 */
+	virtual int register_class_devname(const char *class_devname);
+
+        /**
+	 * Register a class device name, automatically adding device
+	 * class instance suffix if need be.
+	 *
+	 * @param class_devname   Device class name
+	 * @param class_instance  Device class instance from register_class_devname()
+	 * @return		  OK on success, -errno otherwise
+	 */
+	virtual int unregister_class_devname(const char *class_devname, unsigned class_instance);
+
 private:
 	static const unsigned _max_pollwaiters = 8;
 
@@ -488,4 +507,7 @@ private:
 
 } // namespace device
 
+// class instance for primary driver of each class
+#define CLASS_DEVICE_PRIMARY 0
+
 #endif /* _DEVICE_DEVICE_H */