Add beginning basic serial driver

src/kernel/serial.h

@@ -0,0 +1,25 @@
+#pragma once
+/// \file serial.h
+/// Declarations related to serial ports.
+#include <stdint.h>
+
+class serial_port
+{
+public:
+	/// Constructor.
+	/// \arg port   The IO address of the serial port
+	serial_port(uint16_t port);
+
+	serial_port();
+
+	void write(char c);
+	char read();
+
+private:
+	uint16_t m_port;
+
+	bool read_ready();
+	bool write_ready();
+};
+
+extern serial_port g_com1;