Directory structure:

meta-i2s/
├── conf
│   └── layer.conf
└── recipes-kernel
    └── i2s
        ├── files
        │   ├── Makefile
        │   ├── README.md
        │   └── my_loader.c
        └── i2s-rpi-mod.bb

i2s-rpi-mod.bb:

SUMMARY = "i2s kernel module"
LICENSE = "GPLv2"

inherit module

SRC_URI = "file://Makefile \
           file://my_loader.c \
          "

S = "${WORKDIR}"

# The inherit of module.bbclass will automatically name module packages with
# "kernel-module-" prefix as required by the oe-core build environment.

RPROVIDES_${PN} += "my_loader"

layer.conf:

# We have a conf and classes directory, add to BBPATH
BBPATH .= ":${LAYERDIR}"

# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
            ${LAYERDIR}/recipes-*/*/*.bbappend"

BBFILE_COLLECTIONS += "yoctobsp"
BBFILE_PATTERN_yoctobsp = "^${LAYERDIR}/"
BBFILE_PRIORITY_yoctobsp = "5"
LAYERVERSION_yoctobsp = "4"
LAYERSERIES_COMPAT_yoctobsp = "sumo"