feat: Add serial logging (#3)

Reviewed-on: #3

kernel/src/logger/serial.rs

@@ -0,0 +1,28 @@
+use core::fmt;
+
+pub struct SerialPort {
+    port: uart_16550::SerialPort,
+}
+
+impl SerialPort {
+    /// # Safety
+    ///
+    /// unsafe because this function must only be called once
+    pub unsafe fn init() -> Self {
+        let mut port = unsafe { uart_16550::SerialPort::new(0x3F8) };
+        port.init();
+        Self { port }
+    }
+}
+
+impl fmt::Write for SerialPort {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        for char in s.bytes() {
+            match char {
+                b'\n' => self.port.write_str("\r\n").unwrap(),
+                byte => self.port.send(byte),
+            }
+        }
+        Ok(())
+    }
+}