arm: mvebu: Support for 98DX25xx/98DX35xx SoC

Add support for the Allecat5/Alleycat5X SoC. These are L3 switches with
an integrated CPU (referred to as the CnM block in Marvell's
documentation). These have dual ARMv8.2 CPUs (Cortex-A55). This support
has been ported from Marvell's SDK which is based on a much older
version of U-Boot.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
diff --git a/arch/arm/dts/ac5-98dx35xx.dtsi b/arch/arm/dts/ac5-98dx35xx.dtsi
new file mode 100644
index 0000000..2ab72f8
--- /dev/null
+++ b/arch/arm/dts/ac5-98dx35xx.dtsi
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Device Tree For AC5X.
+ *
+ * Copyright (C) 2022 Allied Telesis Labs
+ */
+
+#include "ac5-98dx25xx.dtsi"
+
+/ {
+	model = "Marvell AC5X SoC";
+	compatible = "marvell,ac5x", "marvell,ac5";
+};
+
+&cnm_clock {
+	clock-frequency = <325000000>;
+};