Clone Yocto and required layers:

export BASE=~/projects/signum-pi
mkdir -p $BASE && cd $BASE
git clone -b jethro git://git.yoctoproject.org/poky
cd poky
git clone -b jethro git://git.yoctoproject.org/meta-raspberrypi
git clone -b jethro git://git.openembedded.org/meta-openembedded
git clone -b jethro https://github.com/meta-qt5/meta-qt5.git
git clone -b jethro https://github.com/kovrov/meta-signum.git

Initialize build configuration "build":

cd $BASE
TEMPLATECONF=../poky/meta-signum/conf source poky/oe-init-build-env build

Edit $BASE/build/conf/bblayers.conf so the BBLAYERS variable contains following paths:

POKYDIR := "${@os.path.abspath(os.path.dirname(d.getVar('FILE', True)) + '/../../poky')}"
BBLAYERS ?= "\
 ${POKYDIR}/meta \
 ${POKYDIR}/meta-yocto \
 ${POKYDIR}/meta-openembedded/meta-oe \
 ${POKYDIR}/meta-openembedded/meta-networking \
 ${POKYDIR}/meta-openembedded/meta-python \
 ${POKYDIR}/meta-qt5 \
 ${POKYDIR}/meta-signum \
 ${POKYDIR}/meta-signum/meta-rpi \
 ${POKYDIR}/meta-raspberrypi \
"

Add or update BitBake variables in $BASE/build/conf/local.conf:

MACHINE = "raspberrypi2"
GPU_MEM = "256"
DISTRO_FEATURES_remove = "x11 wayland"
DISTRO_FEATURES_append = " systemd"
VIRTUAL-RUNTIME_init_manager = "systemd"
DISTRO_FEATURES_BACKFILL_CONSIDERED = "sysvinit"
VIRTUAL-RUNTIME_initscripts = ""
PACKAGE_CLASSES = "package_ipk"

The MACHINE variable could be "raspberrypi" or "raspberrypi2". The GPU_MEM variable is used to configure Raspberry Pi GPU memory in megabytes. Optionally DL_DIR variable could be set to a common location so archives downloaded from upstream repositories could be shared between different build configurations.

Packages omxplayer and gstreamer1.0-libav (defined in meta-raspberrypi) depends on libav which has a commercial license. In order to be able to include them in the image, the variable LICENSE_FLAGS_WHITELIST must contain "commercial".

The image name is "qt5-image-signum"

bitbake qt5-image-signum

Generated images located in $BASE/build/tmp/deploy/images/raspberrypi2/. An image could be written to SD card partition with dd tool.

sudo umount /dev/sdx*
sudo dd if=tmp/deploy/images/raspberrypi2/qt5-image-signum-raspberrypi2.rpi-sdimg of=/dev/sdx
sync

Where "sdx" is the name of SD card device on "sysfs". The name could be queried with df -h.

Comprehensive information could be fond on Raspberry Pi Documentation site -- Installing Operating System Images on Linux

Depending on screen model, a specific HDMI mode may be needed. For example http://www.waveshare.com/7inch-HDMI-LCD-B.htm is 800x480 60Hz. Edit config.txt:

hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 800 480 60 6 0 0 0
max_usb_current=1

More details here http://elinux.org/RPiconfig

After image is written to SD card, device is ready to be booted. If ethernet cable is connected, device's IP address should be displayed on the screen. ssh to the device as root without password.

To configure TimeZone manually:

ln -sf /usr/share/zoneinfo/America/Los_Angeles /etc/localtime
/etc/init.d/ntpd stop
ntpdate -s time.nist.gov
/etc/init.d/ntpd start

To force SSH login to use only Public Key Authentication. Append the public keys to /home/root/.ssh/authorized_keys. Edit following section of /etc/ssh/sshd_config:

PasswordAuthentication no

Signum is the application that being started automatically when device is booted. The init script /etc/init.d/signum could be used stop or start the app. QML files are located in /usr/share/signum/.

The meta-qt5 provides an installable Qt5 toolchain and SDK. The recipe name is "meta-toolchain-qt5". It could be built with a BitBake:

bitbake meta-toolchain-qt5

The generated binary installer located in $BASE/build/tmp/deploy/sdk/. It is an interactive installation script:

tmp/deploy/sdk/poky-glibc-x86_64-meta-toolchain-qt5-arm1176jzfshf-vfp-toolchain-1.8.sh -d <dir>

If omitted, the <dir> is "/opt/poky/1.8" which would require running installer with sudo.

To use the toolchain, following environment-setup script must be sourced every time:

source /opt/poky/1.8/environment-setup-arm1176jzfshf-vfp-poky-linux-gnueabi

This information is based on different sources I found all over the Internet, but mostly on very useful articles on http://embarcados.com.br/ and meta-layer code on https://bitbucket.org/embarcados