[RFC Patch v2 03/16] multikernel: Introduce basic multikernel subsystem infrastructure

[Cong Wang <xiyou.wangcong@gmail.com>]

From: Cong Wang <cwang@multikernel.io>

This commit introduces:

* Configuration infrastructure (kernel/multikernel/Kconfig) that adds
  CONFIG_MULTIKERNEL option depending on KEXEC_CORE, it will provide kernfs
  interface for multikernel instance management, device tree based
  resource management, physical memory pool allocation, and kexec integration.

* Core initialization module (kernel/multikernel/core.c) that provides
  basic subsystem initialization using subsys_initcall() to ensure
  multikernel support is initialized after core kernel subsystems.

This foundational commit establishes the basic framework that subsequent
patches will build upon to implement the full multikernel functionality.

Signed-off-by: Cong Wang <cwang@multikernel.io>
---
 kernel/Kconfig.kexec        |  2 ++
 kernel/Makefile             |  1 +
 kernel/multikernel/Kconfig  | 20 ++++++++++++++++++++
 kernel/multikernel/Makefile |  6 ++++++
 kernel/multikernel/core.c   | 17 +++++++++++++++++
 5 files changed, 46 insertions(+)
 create mode 100644 kernel/multikernel/Kconfig
 create mode 100644 kernel/multikernel/Makefile
 create mode 100644 kernel/multikernel/core.c

diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
index 422270d64820..e0fbd7e9af43 100644
--- a/kernel/Kconfig.kexec
+++ b/kernel/Kconfig.kexec
@@ -194,4 +194,6 @@ config CRASH_MAX_MEMORY_RANGES
 	  the computation behind the value provided through the
 	  /sys/kernel/crash_elfcorehdr_size attribute.
 
+source "kernel/multikernel/Kconfig"
+
 endmenu
diff --git a/kernel/Makefile b/kernel/Makefile
index df3dd8291bb6..017ed567f86a 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -56,6 +56,7 @@ obj-y += dma/
 obj-y += entry/
 obj-y += unwind/
 obj-$(CONFIG_MODULES) += module/
+obj-$(CONFIG_MULTIKERNEL) += multikernel/
 
 obj-$(CONFIG_KCMP) += kcmp.o
 obj-$(CONFIG_FREEZER) += freezer.o
diff --git a/kernel/multikernel/Kconfig b/kernel/multikernel/Kconfig
new file mode 100644
index 000000000000..0e61fd2e505a
--- /dev/null
+++ b/kernel/multikernel/Kconfig
@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Multikernel configuration
+#
+
+config MULTIKERNEL
+	bool "Multikernel support"
+	depends on KEXEC_CORE
+	help
+	  Enable multikernel support, which allows running multiple kernel
+	  instances simultaneously with resource isolation and inter-kernel
+	  communication capabilities.
+
+	  This feature provides:
+	  - Sysfs interface for multikernel instance management
+	  - Device tree based resource specification
+	  - Memory pool management for kernel instances
+	  - Integration with kexec for kernel loading
+
+	  If unsure, say N.
diff --git a/kernel/multikernel/Makefile b/kernel/multikernel/Makefile
new file mode 100644
index 000000000000..950bace927a0
--- /dev/null
+++ b/kernel/multikernel/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for multikernel support
+#
+
+obj-y += core.o
diff --git a/kernel/multikernel/core.c b/kernel/multikernel/core.c
new file mode 100644
index 000000000000..218424d59cc3
--- /dev/null
+++ b/kernel/multikernel/core.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Multikernel Technologies, Inc. All rights reserved
+ */
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/multikernel.h>
+
+static int __init multikernel_init(void)
+{
+	pr_info("Multikernel support initialized\n");
+	return 0;
+}
+
+/* Initialize multikernel after core kernel subsystems are ready */
+subsys_initcall(multikernel_init);
-- 
2.34.1