Kernel: Improve the aarch64 kernel source files disk layout

Kernel/Arch/aarch64/RPi/UART.h

@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2021, Nico Weber <thakis@chromium.org>
+ * Copyright (c) 2021, Jesse Buhagiar <jooster669@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+
+namespace Prekernel {
+
+struct UARTRegisters;
+
+// Abstracts the PL011 UART on a Raspberry Pi.
+// (The BCM2711 on a Raspberry Pi 4 has five PL011 UARTs; this is always the first of those.)
+class UART {
+public:
+    static UART& the();
+
+    void send(u32 c);
+    u32 receive();
+
+    void print_str(char const* s)
+    {
+        while (*s)
+            send(*s++);
+    }
+    void print_num(u64 n)
+    {
+        char buf[21];
+        int i = 0;
+        do {
+            buf[i++] = (n % 10) + '0';
+            n /= 10;
+        } while (n);
+        for (i--; i >= 0; i--)
+            send(buf[i]);
+    }
+
+    void print_hex(u64 n)
+    {
+        char buf[17];
+        static char const* digits = "0123456789ABCDEF";
+        int i = 0;
+        do {
+            buf[i++] = digits[n % 16];
+            n /= 16;
+        } while (n);
+        send(static_cast<u32>('0'));
+        send(static_cast<u32>('x'));
+        buf[16] = '\0';
+        for (i--; i >= 0; i--) {
+            send(buf[i]);
+        }
+    }
+
+private:
+    UART();
+
+    void set_baud_rate(int baud_rate, int uart_frequency_in_hz);
+    void wait_until_we_can_send();
+    void wait_until_we_can_receive();
+
+    UARTRegisters volatile* m_registers;
+};
+
+}