  The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will
observe several Deep Drilling Fields (DDFs) to a greater depth and with a more
rapid cadence than the main survey. In this paper, we describe the
``DeepDrill'' survey, which used the Spitzer Space Telescope Infrared Array
Camera (IRAC) to observe three of the four currently defined DDFs in two bands,
centered on 3.6 $\mu$m and 4.5 $\mu$m. These observations expand the area which
was covered by an earlier set of observations in these three fields by the
Spitzer Extragalactic Representative Volume Survey (SERVS). The combined
DeepDrill and SERVS data cover the footprints of the LSST DDFs in the Extended
Chandra Deep Field-South field (ECDFS), the ELAIS-S1 field (ES1), and the XMM
Large-Scale Structure Survey field (XMM-LSS). The observations reach an
approximate $5\sigma$ point-source depth of 2 $\mu$Jy (corresponding to an AB
magnitude of 23.1; sufficient to detect a 10$^{11} M_{\odot}$ galaxy out to
$z\approx 5$) in each of the two bands over a total area of $\approx
29\,$deg$^2$. The dual-band catalogues contain a total of 2.35 million sources.
In this paper we describe the observations and data products from the survey,
and an overview of the properties of galaxies in the survey. We compare the
source counts to predictions from the SHARK semi-analytic model of galaxy
formation. We also identify a population of sources with extremely red
([3.6]$-$[4.5] $>1.2$) colours which we show mostly consists of highly-obscured
active galactic nuclei.
