kbuild: introduce destination-y for exported headers

xtensa and arm have asked for a possibility to export headers
and locate them in a specific directory when exported.
Introduce destiantion-y to support this.

This patch in additiona adds some limited
documentation for the variables used for exported headers.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Oskar Schirmer <os@emlix.com>
Cc: Mikael Starvik <mikael.starvik@axis.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/scripts/Makefile.headersinst b/scripts/Makefile.headersinst
index 612dc13ddd85..095cfc8b9dbf 100644
--- a/scripts/Makefile.headersinst
+++ b/scripts/Makefile.headersinst
@@ -14,6 +14,8 @@ _dst := $(if $(dst),$(dst),$(obj))
 kbuild-file := $(srctree)/$(obj)/Kbuild
 include $(kbuild-file)
 
+_dst := $(if $(destination-y),$(destination-y),$(_dst))
+
 include scripts/Kbuild.include
 
 install       := $(INSTALL_HDR_PATH)/$(_dst)