Linux 4.12, buildroot 2017.08, Ubuntu 17.10.

17.10 failed with a similar message to: http://patchwork.ozlabs.org/patch/772848/
but applying that patch did not solve it, apparently there were fixes already
on later versions of the tracked package.

Update .gitmodules to ignore patches we apply to Buildroot.

maintainers.md

@@ -0,0 +1,27 @@
+# Maintainers
+
+## How to update the Linux kernel version?
+
+TODO I can only do it "easily" if the kernel headers are supported, check `buildroot/package/linux-headers/Config.in.host` to see if `BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_12` is there. Once you've found a supported version:
+
+    cd linux
+    git rebase --onto v4.12 v4.9.6
+    # git rebase --onto <new> <old base with our patches on top>
+
+And on `buildroot_config_fragment` edit:
+
+    BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.12"
+    BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_12=y
+
+## How to add new Buildroot options?
+
+    cd buildroot/output.x86_64~
+    make menuconfig
+
+Hit `/` and search for the settings.
+
+Save and quit.
+
+    diff .config.olg .config
+
+Copy and paste the diff additions to `buildroot_config_fragment`.