Kbuild: introduce Makefile in arch/$ARCH/

Introduce a Makefile under arch/$ARCH/ and include it in the
top Makefile (similar to Linux kernel). This allows further
refactoringi like moving architecture-specific code out of global
makefiles, deprecating config variables (CPU, CPUDIR, SOC) or
deprecating arch/$ARCH/config.mk.

In contrary to Linux kernel, U-Boot defines the ARCH variable by
Kconfig, thus the arch Makefile can only included conditionally
after the top config.mk.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Acked-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/arc/Makefile b/arch/arc/Makefile
new file mode 100644
index 0000000..de25cc9
--- /dev/null
+++ b/arch/arc/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/arc/cpu/$(CPU)/start.o
+
+libs-y += arch/arc/cpu/$(CPU)/
+libs-y += arch/arc/lib/
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
new file mode 100644
index 0000000..ebb7dc3
--- /dev/null
+++ b/arch/arm/Makefile
@@ -0,0 +1,29 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/arm/cpu/$(CPU)/start.o
+
+ifeq ($(CONFIG_SPL_BUILD),y)
+ifneq ($(CONFIG_SPL_START_S_PATH),)
+head-y := $(CONFIG_SPL_START_S_PATH:"%"=%)/start.o
+endif
+endif
+
+libs-y += arch/arm/cpu/$(CPU)/
+libs-y += arch/arm/cpu/
+libs-y += arch/arm/lib/
+
+ifeq ($(CONFIG_SPL_BUILD),y)
+ifneq (,$(CONFIG_MX23)$(CONFIG_MX35)$(filter $(SOC), mx25 mx27 mx5 mx6 mx31 mx35))
+libs-y += arch/arm/imx-common/
+endif
+else
+ifneq (,$(filter $(SOC), mx25 mx27 mx5 mx6 mx31 mx35 mxs vf610))
+libs-y += arch/arm/imx-common/
+endif
+endif
+
+ifneq (,$(filter $(SOC), armada-xp kirkwood))
+libs-y += arch/arm/mvebu-common/
+endif
diff --git a/arch/avr32/Makefile b/arch/avr32/Makefile
new file mode 100644
index 0000000..e9b3184
--- /dev/null
+++ b/arch/avr32/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/avr32/cpu/start.o
+
+libs-y += arch/avr32/cpu/
+libs-y += arch/avr32/lib/
diff --git a/arch/blackfin/Makefile b/arch/blackfin/Makefile
new file mode 100644
index 0000000..787475e
--- /dev/null
+++ b/arch/blackfin/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/blackfin/cpu/start.o
+
+libs-y += arch/blackfin/cpu/
+libs-y += arch/blackfin/lib/
diff --git a/arch/m68k/Makefile b/arch/m68k/Makefile
new file mode 100644
index 0000000..aa3d2fa
--- /dev/null
+++ b/arch/m68k/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/m68k/cpu/$(CPU)/start.o
+
+libs-y += arch/m68k/cpu/$(CPU)/
+libs-y += arch/m68k/lib/
diff --git a/arch/microblaze/Makefile b/arch/microblaze/Makefile
new file mode 100644
index 0000000..ae4adc2
--- /dev/null
+++ b/arch/microblaze/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/microblaze/cpu/start.o
+
+libs-y += arch/microblaze/cpu/
+libs-y += arch/microblaze/lib/
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
new file mode 100644
index 0000000..1907b57
--- /dev/null
+++ b/arch/mips/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/mips/cpu/$(CPU)/start.o
+
+libs-y += arch/mips/cpu/$(CPU)/
+libs-y += arch/mips/lib/
diff --git a/arch/nds32/Makefile b/arch/nds32/Makefile
new file mode 100644
index 0000000..e1eccba
--- /dev/null
+++ b/arch/nds32/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/nds32/cpu/$(CPU)/start.o
+
+libs-y += arch/nds32/cpu/$(CPU)/
+libs-y += arch/nds32/lib/
diff --git a/arch/nios2/Makefile b/arch/nios2/Makefile
new file mode 100644
index 0000000..18685a9
--- /dev/null
+++ b/arch/nios2/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/nios2/cpu/start.o
+
+libs-y += arch/nios2/cpu/
+libs-y += arch/nios2/lib/
diff --git a/arch/openrisc/Makefile b/arch/openrisc/Makefile
new file mode 100644
index 0000000..c4da3ce
--- /dev/null
+++ b/arch/openrisc/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/openrisc/cpu/start.o
+
+libs-y += arch/openrisc/cpu/
+libs-y += arch/openrisc/lib/
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
new file mode 100644
index 0000000..8aa1d60
--- /dev/null
+++ b/arch/powerpc/Makefile
@@ -0,0 +1,11 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/powerpc/cpu/$(CPU)/start.o
+head-$(CONFIG_4xx) += arch/powerpc/cpu/ppc4xx/resetvec.o
+head-$(CONFIG_MPC85xx) += arch/powerpc/cpu/mpc85xx/resetvec.o
+
+libs-y += arch/powerpc/cpu/$(CPU)/
+libs-y += arch/powerpc/cpu/
+libs-y += arch/powerpc/lib/
diff --git a/arch/sandbox/Makefile b/arch/sandbox/Makefile
new file mode 100644
index 0000000..23fdcdb
--- /dev/null
+++ b/arch/sandbox/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/sandbox/cpu/start.o
+
+libs-y += arch/sandbox/cpu/
+libs-y += arch/sandbox/lib/
diff --git a/arch/sh/Makefile b/arch/sh/Makefile
new file mode 100644
index 0000000..ca55fac
--- /dev/null
+++ b/arch/sh/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/sh/cpu/$(CPU)/start.o
+
+libs-y += arch/sh/cpu/$(CPU)/
+libs-y += arch/sh/lib/
diff --git a/arch/sparc/Makefile b/arch/sparc/Makefile
new file mode 100644
index 0000000..2d4c971
--- /dev/null
+++ b/arch/sparc/Makefile
@@ -0,0 +1,8 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/sparc/cpu/$(CPU)/start.o
+
+libs-y += arch/sparc/cpu/$(CPU)/
+libs-y += arch/sparc/lib/
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
new file mode 100644
index 0000000..36a6018
--- /dev/null
+++ b/arch/x86/Makefile
@@ -0,0 +1,12 @@
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+head-y := arch/x86/cpu/start.o
+ifeq ($(CONFIG_SPL_BUILD),y)
+head-y += arch/x86/cpu/start16.o
+head-y += arch/x86/cpu/resetvec.o
+endif
+
+libs-y += arch/x86/cpu/
+libs-y += arch/x86/lib/