MIPS: Share generic kernel code with other architecture

Some architectures might seek to utilize a significant portion of the
generic kernel code while maintaining independence from the generic
kernel due to specific peculiarities.

This patch allows for the reuse of core code, preventing unnecessary
duplication.

Suggested-by: Thomas Bogendoerfer <[e-mail]>
Reviewed-by: Jiaxun Yang <[e-mail]>
Signed-off-by: Gregory CLEMENT <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/Kbuild

···
 # mips object files
 # The object files are linked as core-y files would be linked
 
+obj-y += generic/
 obj-y += kernel/
 obj-y += mm/
 obj-y += net/

arch/mips/Kconfig

···
 config MIPS_GENERIC
 	bool
 
+config MACH_GENERIC_CORE
+	bool
+
 config MACH_INGENIC
 	bool
 	select SYS_SUPPORTS_32BIT_KERNEL
···
 	select DMA_NONCOHERENT
 	select HAVE_PCI
 	select IRQ_MIPS_CPU
+	select MACH_GENERIC_CORE
 	select MIPS_AUTO_PFN_OFFSET
 	select MIPS_CPU_SCACHE
 	select MIPS_GIC
···
 	bool "Ingenic SoC based machines"
 	select MIPS_GENERIC
 	select MACH_INGENIC
+	select MACH_GENERIC_CORE
 	select SYS_SUPPORTS_ZBOOT_UART16550
 	select CPU_SUPPORTS_CPUFREQ
 	select MIPS_EXTERNAL_TIMER
···
 config MACH_REALTEK_RTL
 	bool "Realtek RTL838x/RTL839x based machines"
 	select MIPS_GENERIC
+	select MACH_GENERIC_CORE
 	select DMA_NONCOHERENT
 	select IRQ_MIPS_CPU
 	select CSRC_R4K

arch/mips/generic/Makefile

···
 # Author: Paul Burton <[e-mail]>
 #
 
-obj-y += init.o
-obj-y += irq.o
-obj-y += proc.o
+obj-$(CONFIG_MACH_GENERIC_CORE) += init.o
+obj-$(CONFIG_MACH_GENERIC_CORE) += irq.o
+obj-$(CONFIG_MACH_GENERIC_CORE) += proc.o
 
 obj-$(CONFIG_YAMON_DT_SHIM)		+= yamon-dt.o
 obj-$(CONFIG_LEGACY_BOARD_SEAD3)	+= board-sead3.o