Separate kernel code from test code

Eventually I want the kernel to be loaded from the SD card as well, but
it still needs to separate from user programs.

At some point there should be a folder just for the BIOS, which should
read from the boot block of the SD card and start executing, and thats
it.

sw/kernel/devices/interrupt.h

@@ -0,0 +1,15 @@
+#ifndef _INTERRUPT_H
+#define _INTERRUPT_H
+
+#include <stdint.h>
+
+#define BUTTON  (1 << 0)
+#define UART    (1 << 1)
+
+void irq_int();
+void nmi_int();
+
+uint8_t irq_get_status();
+void irq_set_status(uint8_t);
+
+#endif