mips: mtmips: add support for MediaTek MT7621 SoC

This patch adds support for MediaTek MT7621 SoC.
All files are dedicated for u-boot.

The default build target is u-boot-mt7621.bin.

The specification of this chip:
https://www.mediatek.com/products/homenetworking/mt7621

Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/mach-mtmips/mt7621/spl/launch.h b/arch/mips/mach-mtmips/mt7621/spl/launch.h
new file mode 100644
index 0000000..f34250d
--- /dev/null
+++ b/arch/mips/mach-mtmips/mt7621/spl/launch.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2022 MediaTek Inc. All rights reserved.
+ *
+ * Author: Weijie Gao <weijie.gao@mediatek.com>
+ */
+
+#ifndef _LAUNCH_H_
+#define _LAUNCH_H_
+
+#ifndef __ASSEMBLY__
+
+struct cpulaunch_t {
+	unsigned long pc;
+	unsigned long gp;
+	unsigned long sp;
+	unsigned long a0;
+	unsigned long _pad[3]; /* pad to cache line size to avoid thrashing */
+	unsigned long flags;
+};
+
+extern char launch_wait_code_start;
+extern char launch_wait_code_end;
+
+void join_coherent_domain(int ncores);
+void boot_vpe1(void);
+
+#else
+
+#define	LAUNCH_PC		0
+#define	LAUNCH_GP		4
+#define	LAUNCH_SP		8
+#define	LAUNCH_A0		12
+#define	LAUNCH_FLAGS		28
+
+#endif
+
+#define LOG2CPULAUNCH		5
+
+#define LAUNCH_FREADY		1
+#define LAUNCH_FGO		2
+#define LAUNCH_FGONE		4
+
+#define LAUNCH_WAITCODE		0x00000d00
+#define SCRLAUNCH		0x00000e00
+#define CPULAUNCH		0x00000f00
+#define NCPULAUNCH		8
+
+/* Polling period in count cycles for secondary CPU's */
+#define LAUNCHPERIOD		10000
+
+#endif /* _LAUNCH_H_ */