Add PL011 UART driver

A minimal PL011 driver containing necessary functions
to print to UART. Based on the assembly implementation
found in TF-A (hash: 39bcbeac9c8c20ae660cb6d9e825ceb01e6144e7;
file: drivers/arm/pl011/aarch64/pl011_console.S).

Signed-off-by: Gabor Toth <gabor.toth2@arm.com>
Signed-off-by: Gabor Ambrus <gabor.ambrus@arm.com>
Change-Id: I644fb011b2b9a68aa09e8cc3a09ebd8b9576bb30
diff --git a/platform/drivers/arm/uart/uart_decl.h b/platform/drivers/arm/uart/uart_decl.h
new file mode 100644
index 0000000..19bf95f
--- /dev/null
+++ b/platform/drivers/arm/uart/uart_decl.h
@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2017-2023, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * This is a modified version of the uart platform driver from trusted-firmware-a.
+ * The code has been modified to allow the peripheral to be accessed by S-EL0 at
+ * an arbitrary virtual address.
+ */
+
+#ifndef UART_DECL_H
+#define UART_DECL_H
+
+#include <stdint.h>
+
+int uart_deinit(uintptr_t addr);
+int uart_init(uintptr_t addr);
+void uflush(uintptr_t addr);
+void uputc(uint8_t ch, uintptr_t addr);
+
+#endif /* UART_DECL_H */