Added support for Sonata's joystick.

sdk/include/platform/sunburst/platform-gpio.hh

diff --git a/sdk/include/platform/sunburst/platform-gpio.hh b/sdk/include/platform/sunburst/platform-gpio.hh
index 3f97f8d..02f1e14 100644
--- a/sdk/include/platform/sunburst/platform-gpio.hh
+++ b/sdk/include/platform/sunburst/platform-gpio.hh
@@ -3,6 +3,23 @@
 #include <stdint.h>
 
 /**
+ * Represents the state of the Sonata's joystick.
+ *
+ * Note, that up to three of the bits may be asserted at any given time.
+ * There may be up to two cardinal directions asserted when the joystick is
+ * pushed in a diagonal and the joystick may be pressed while being pushed in a
+ * given direction.
+ */
+enum class SonataJoystick : uint8_t
+{
+	Left    = 1 << 0,
+	Up      = 1 << 1,
+	Pressed = 1 << 2,
+	Down    = 1 << 3,
+	Right   = 1 << 4,
+};
+
+/**
  * A Simple Driver for the Sonata's GPIO.
  *
  * Documentation source can be found at:
@@ -58,4 +75,12 @@
 	{
 		output = output ^ led_bit(index);
 	}
+
+	/**
+	 * Returns the state of the joystick.
+	 */
+	SonataJoystick read_joystick() volatile
+	{
+		return static_cast<SonataJoystick>(input & 0x1f);
+	}
 };