lib: utils: Add LiteX UART support

Add support for the UART provided by the LiteX SoC
framework (https://github.com/enjoy-digital/litex),
based on its FDT info (described in the Linux tree at
Documentation/devicetree/bindings/serial/litex,liteuart.yaml).

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>

lib/utils/serial/fdt_serial_litex.c

@@ -0,0 +1,39 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Gabriel Somlo
+ *
+ * Authors:
+ *   Gabriel Somlo <gsomlo@gmail.com>
+ */
+
+#include <sbi/sbi_error.h>
+#include <sbi_utils/fdt/fdt_helper.h>
+#include <sbi_utils/serial/fdt_serial.h>
+#include <sbi_utils/serial/litex-uart.h>
+
+static int serial_litex_init(void *fdt, int nodeoff,
+			     const struct fdt_match *match)
+{
+	uint64_t reg_addr, reg_size;
+	int rc;
+
+	if (nodeoff < 0 || !fdt)
+		return SBI_ENODEV;
+
+	rc = fdt_get_node_addr_size(fdt, nodeoff, 0, &reg_addr, &reg_size);
+	if (rc < 0 || !reg_addr || !reg_size)
+		return SBI_ENODEV;
+
+	return litex_uart_init(reg_addr);
+}
+
+static const struct fdt_match serial_litex_match[] = {
+	{ .compatible = "litex,liteuart" },
+	{ },
+};
+
+struct fdt_serial fdt_serial_litex = {
+	.match_table = serial_litex_match,
+	.init = serial_litex_init
+};