We use a directory under arch/$ARCH/boot/dts as an include path
that has links outside of the subtree to find dt-bindings from under
include/dt-bindings. That's been working well, but new DT architectures
haven't been adding them by default.

Recently there's been a desire to share some of the DT material between
arm and arm64, which originally caused developers to create symlinks or
relative includes between the subtrees. This isn't ideal -- it breaks
if the DT files aren't stored in the exact same hierarchy as the kernel
tree, and generally it's just icky.

As a somewhat cleaner solution we decided to add a $ARCH/ prefix link
once, and allow DTS files to reference dtsi (and dts) files in other
architectures that way.

Original approach was to create these links under each architecture,
but it lead to the problem of recursive symlinks.

As a remedy, move the include link directories out of the architecture
trees into a common location. At the same time, they can now share one
directory and one dt-bindings/ link as well.

Fixes: 4027494ae6e3 ('ARM: dts: add arm/arm64 include symlinks')
Reported-by: Russell King
Reported-by: Omar Sandoval
Reviewed-by: Heiko Stuebner
Reviewed-by: Masahiro Yamada
Tested-by: Heiko Stuebner
Acked-by: Rob Herring
Cc: Heiko Stuebner
Cc: Mark Rutland
Cc: Russell King
Cc: Catalin Marinas
Cc: Will Deacon
Cc: Mikael Starvik
Cc: Jesper Nilsson
Cc: James Hogan
Cc: Ralf Baechle
Cc: Benjamin Herrenschmidt
Cc: Paul Mackerras
Cc: Michael Ellerman
Cc: Frank Rowand
Cc: linux-arch
Signed-off-by: Olof Johansson