Build LinuxTV on Raspbian?

On Raspbian/wheezy with 3.18.7 kernel I ran the basic approach and end up somewhere here:

...
v4l-cx231xx-avcore-01.fw
v4l-cx23418-apu.fw
v4l-cx23418-cpu.fw
v4l-cx23418-dig.fw
v4l-cx23885-avcore-01.fw
v4l-cx23885-enc-broken.fw
v4l-cx25840.fw
******************
* Start building *
******************
make -C /home/pi/media_build/v4l allyesconfig
make[1]: Entering directory '/home/pi/media_build/v4l'
make[2]: Entering directory '/home/pi/media_build/linux'
Applying patches for kernel 3.18.7-v7+
patch -s -f -N -p1 -i ../backports/api_version.patch
patch -s -f -N -p1 -i ../backports/pr_fmt.patch
patch -s -f -N -p1 -i ../backports/debug.patch
patch -s -f -N -p1 -i ../backports/drx39xxj.patch
patch -s -f -N -p1 -i ../backports/v4.0_dma_buf_export.patch
patch -s -f -N -p1 -i ../backports/v4.0_drop_trace.patch
Patched drivers/media/dvb-core/dvbdev.c
Patched drivers/media/v4l2-core/v4l2-dev.c
Patched drivers/media/rc/rc-main.c
make[2]: Leaving directory '/home/pi/media_build/linux' ./scripts/make_kconfig.pl /lib/modules/3.18.7-v7+/build /lib/modules/3.18.7-v7+/build 1
Preparing to compile for kernel version 3.18.7
File not found: /lib/modules/3.18.7-v7+/build/.config
at ./scripts/make_kconfig.pl line 33, <IN> line 4.
Makefile:366: recipe for target 'allyesconfig' failed
make[1]: *** [allyesconfig] Error 2
make[1]: Leaving directory '/home/pi/media_build/v4l'
Makefile:26: recipe for target 'allyesconfig' failed
make: *** [allyesconfig] Error 2
can't select all drivers at ./build line 490.

I am clueless what goes wrong, pointers appreciated.
A generic google search regarding kernel module compiles on RasPis points some kernel config files are not in place where they should be, but I don't know how to tackle the issue.

Dex

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