cmake: support hw model v2 in arch/Kconfig tree

This commit introduces support for Zephyr hw model v2 in the arch
Kconfig tree.

The hw model v2 requires Kconfig trees to be self-contained, meaning
that the have no Kconfig references outside the tree itself.

For hw model v2, the architecture of a board / SoC is not known until
the Kconfig tree and config file has been parsed.
There provide a new arch/Kconfig.v2 file to support loading of all arch
Kconfigs. Hw model v1 is now placed in arch/Kconfig.v1 and includes
only the arch Kconfig files determined by the arch of the board.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

arch/Kconfig

@@ -8,8 +8,10 @@
 # Include these first so that any properties (e.g. defaults) below can be
 # overridden (by defining symbols in multiple locations)
 
-# Note: $ARCH might be a glob pattern
-source "$(ARCH_DIR)/$(ARCH)/Kconfig"
+source "$(ARCH_DIR)/Kconfig.$(HWM_SCHEME)"
+
+# ToDo: Generate a Kconfig.arch for loading of additional arch in HWMv2.
+osource "$(KCONFIG_BINARY_DIR)/Kconfig.arch"
 
 # Architecture symbols
 #

arch/Kconfig.v1

@@ -0,0 +1,5 @@
+# Copyright (c) 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+# Note: $ARCH might be a glob pattern
+source "$(ARCH_DIR)/$(ARCH)/Kconfig"

arch/Kconfig.v2

@@ -0,0 +1,5 @@
+# Copyright (c) 2023 Nordic Semiconductor ASA
+
+# SPDX-License-Identifier: Apache-2.0
+
+source "$(KCONFIG_BINARY_DIR)/arch/Kconfig"