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/irq.c

@@ -0,0 +1,24 @@
+
+#include <stdint.h>
+#include <conio.h>
+
+#include "devices/interrupt.h"
+#include "devices/uart.h"
+
+char lastchar;
+
+
+void handle_irq() {
+    uint8_t status;
+
+    status = irq_get_status();
+
+    if (status & BUTTON) {
+        cputs("Button Interrupt!\n");
+        irq_set_status(status & ~BUTTON);
+    }
+    if (status & UART) {
+        lastchar = uart_rxb();
+        irq_set_status(status & ~UART);
+    }
+}