feat(drivers): add port I/O helpers and serial COM1 driver

src/serial.c

@@ -0,0 +1,36 @@
+#include "serial.h"
+#include "ports.h"
+
+#define comPort1 0x3F8
+
+static bool transmitEmpty(void)
+{
+    return (inb(comPort1 + 5) & 0x20) != 0;
+}
+
+void serialInit(void)
+{
+    outb(comPort1 + 1, 0x00);
+    outb(comPort1 + 3, 0x80);
+    outb(comPort1 + 0, 0x01);
+    outb(comPort1 + 1, 0x00);
+    outb(comPort1 + 3, 0x03);
+    outb(comPort1 + 2, 0xC7);
+    outb(comPort1 + 4, 0x0B);
+}
+
+void serialWrite(char c)
+{
+    if (c == '\n') {
+        while (!transmitEmpty()) { }
+        outb(comPort1, '\r');
+    }
+    while (!transmitEmpty()) { }
+    outb(comPort1, (uint8)c);
+}
+
+void serialWriteString(const char* str)
+{
+    while (*str)
+        serialWrite(*str++);
+}