Hi Mark.

Some review feedback.

I recommend to keep the above list sorted alphabetically - to minimize merge conflicts.
But alas no-one follows this recommendation - but this should not prevent you from doing so.

+config GENERIC_FIND_NEXT_BIT
+	def_bool y

Commit: 63e424c84429903c92a0f1e9654c31ccaf6694d0 removed use of
GENERIC_FIND_*.
They also need to be removed from the select above - all
og GENERIC_FIND_*

+config BIG_KERNEL
+	bool "Build a big kernel"
+	help
+	  The C6X function call instruction has a limited range of +/- 2MiB.
+	  This is sufficient for most kernels, but some kernel configurations
+	  with lots of compiled-in functionality may require a larger range
+	  for function calls. Use this option to have the compiler generate
+	  function calls with 32-bit range. This will make the kernel both
+	  larger and slower.
+
+	  If unsure, say N.

To preserve namespace please prefix all C6X specific config symbols with C6X_.
This is true for several symbols.
Btw. I was briefly thinking on BKL when I saw this one :-)

+config FORCE_MAX_ZONEORDER
+	int
+	default "13"

help text is missing. This is the case for several options.

If it is obvious for you what it is - then it should be simple to
write a few lines about it.

+
+menu "Bus options (PCI, PCMCIA, EISA, MCA, ISA)"
+
+config PCI
+	bool "PCI support"
+	help
+	  Support for PCI bus.
+endmenu

I expect you to drop this.
But in general do not refer to stuff that is not valid for your arch.
I guess you do not have ISA either.

No need for a dedicated Kconfig.debug file for a single option.

I am missing sparse support:

CHECKFLAGS += ...

+
+ifdef CONFIG_CPU_BIG_ENDIAN
+KBUILD_CFLAGS   += -mbig-endian
+KBUILD_AFLAGS	+= -mbig-endian
+LINKFLAGS	+= -mbig-endian
+KBUILD_LDFLAGS	+= -mbig-endian
+LDFLAGS	+= -EB

Mixed use of tabs and space for indent.
As tabs has special semantic in Makefile avoid using
tabs for indent. I personally restrain from using tabs
in Makefile due to this. But this is a personal thing.
Do what you prefer - but be consistent.

+endif
+
+head-y		:= arch/c6x/kernel/head.o
+core-y		+= arch/c6x/kernel/ arch/c6x/mm/ arch/c6x/platforms/
+libs-y		+= arch/c6x/lib/
+
+# Default to vmlinux.bin, override when needed
+all: vmlinux.bin
+
+boot := arch/$(ARCH)/boot
+
+# With make 3.82 we cannot mix normal and wildcard targets
+BOOT_TARGETS1 = vmlinux.bin
+BOOT_TARGETS2 = dtbImage.%
+
+$(BOOT_TARGETS1): vmlinux
+	$(Q)$(MAKE) $(build)=$(boot) $(patsubst %,$(boot)/%,$@)
+$(BOOT_TARGETS2): vmlinux
+	$(Q)$(MAKE) $(build)=$(boot) $(patsubst %,$(boot)/%,$@)

No need for the two BOOT_TARGETS variables. We try to be explicit when we can.
But you need to add both rules due to make semantics as you also
document.

+
+archclean:
+	$(Q)$(MAKE) $(clean)=$(boot)
+
+define archhelp
+  @echo '  *_defconfig     - Select default config from arch/$(ARCH)/configs'
+  @echo '  vmlinux.bin     - Binary kernel image (arch/$(ARCH)/boot/vmlinux.bin)'
+  @echo '  dtbImage.<dt>   - ELF image with $(arch)/boot/dts/<dt>.dts linked in'
+  @echo '                  - stripped elf with fdt blob'
+endef

*_defconfig is already covered by the normal "make help" - no need to add them twice.

You never pass the "all" target to the boot makefile - so this line can be dropped.

+
+hostprogs-y := install-dtb
+
+$(obj)/vmlinux.bin: vmlinux
+	$(OBJCOPY) -O binary $< $@

See how x86 handle objcopy.
This is a much nicer output.

+
+
+$(obj)/dtbImage.%: vmlinux $(obj)/install-dtb $(obj)/%.dtb
+	cp vmlinux $@
+	$(obj)/install-dtb $(obj)/$*.dtb $@

This can be made nicer to using more kbuild support.

+
+clean-files := $(obj)/*.dtb
+
+DTC_FLAGS ?= -p 1024
+
+$(obj)/%.dtb: $(src)/dts/%.dts FORCE
+	$(call cmd,dtc)

Everyone and their cousins seems to like the style with
continued lines in Makefile.
But using the following is IMO more readable and less errorprone:

obj-y := process.o traps.o irq.o signal.o ptrace.o
obj-y += setup.o sys_c6x.o time.o devicetree.o
obj-y += switch_to.o entry.o vectors.o c6x_ksyms.o
obj-y += soc.o

Or maybe even like this:
obj-y += c6x_ksyms.o
obj-y += devicetree.o
obj-y += entry.o
obj-y += irq.o
obj-y += ptrace.o
obj-y := process.o
obj-y += setup.o
obj-y += signal.o
obj-y += soc.o
obj-y += sys_c6x.o
obj-y += switch_to.o
obj-y += traps.o
obj-y += time.o
obj-y += vectors.o

then there is room for a comment if you have something to say.
We use the "one assignment per line" in many places. the
extra lines does not matter.

I do not see this used - can it be deleted?

+#include <asm-generic/vmlinux.lds.h>
+#include <asm/thread_info.h>
+#include <asm/page.h>
+
+ENTRY(_c_int00)
+
+#if defined(CONFIG_CPU_BIG_ENDIAN)
+jiffies = jiffies_64 + 4;
+#else
+jiffies = jiffies_64;
+#endif
+
+#define	READONLY_SEGMENT_START	\
+	. = PAGE_OFFSET;
+#define	READWRITE_SEGMENT_START	\
+	. = ALIGN(128);		\
+	_data_lma = .;
+
+SECTIONS
+{
+	/*
+	 * Start kernel read only segment
+	 */
+	READONLY_SEGMENT_START
+
+	.vectors :
+	{
+		VMLINUX_SYMBOL(_vectors_start) = .;
+		*(.vectors)
+		. = ALIGN(0x400);
+		VMLINUX_SYMBOL(_vectors_end) = .;
+	}

You can drop VMLINUX_SYMBOL in the arch specific part
of vmlinux.lds.h - it is invented for the braindead tool-chains that
add an "_" in front of all symbols.

If you insist on using VMLINUX_SYMBOL then be consistent.
It is not used for __machine_desc_start

+
+	. = ALIGN(0x1000);
+	.cmdline : { *(.cmdline) }

Please follow C syntax - like this:

	.cmdline : {
		*(.cmdline)
	}

This is what we do in (almost) all linker scripts these days.
And consistensy is a good thing here.

+
+	/*
+	 * This section contains data which may be shared with other
+	 * cores. It needs to be a fixed offset from PAGE_OFFSET
+	 * regardless of kernel configuration.
+	 */
+	.virtio_ipc_dev : { *(.virtio_ipc_dev) }

C style.

+
+
+	STABS_DEBUG
+
+	DWARF_DEBUG

Is STABS _and_ DWARF both required?
Not a big deal - but is STABS is not supported by your tool-chain
then drop it.

+	/DISCARD/ : {
+		  EXIT_TEXT
+		  EXIT_DATA
+		  EXIT_CALL
+		  *(.discard)
+		  *(.discard.*)
+		  *(.interp)
+	}

I assume you did not use DISCARDS due to "*(.interp)".

+# Makefile for arch/c6x/lib/
+#
+
+lib-y  := divu.o divi.o pop_rts.o push_rts.o remi.o remu.o strasgi.o llshru.o \
+	  llshr.o llshl.o negll.o mpyll.o divull.o divremi.o divremu.o

Multi line..

Kill obsolete comments.

+
+obj-y	 := init.o dma-coherent.o

	Sam