  IoT systems are becoming an essential part of our environment. Smart cities,
smart manufacturing, augmented reality, and self-driving cars are just some
examples of the wide range of domains, where the applicability of such systems
has been increasing rapidly. These IoT use cases often require simultaneous
access to geographically distributed arrays of sensors, and heterogeneous
remote, local as well as multi-cloud computational resources. This gives birth
to the extended Cloud-to-Things computing paradigm. The emergence of this new
paradigm raised the quintessential need to extend the orchestration
requirements i.e., the automated deployment and run-time management) of
applications from the centralised cloud-only environment to the entire spectrum
of resources in the Cloud-to-Things continuum. In order to cope with this
requirement, in the last few years, there has been a lot of attention to the
development of orchestration systems in both industry and academic
environments. This paper is an attempt to gather the research conducted in the
orchestration for the Cloud-to-Things continuum landscape and to propose a
detailed taxonomy, which is then used to critically review the landscape of
existing research work. We finally discuss the key challenges that require
further attention and also present a conceptual framework based on the
conducted analysis.
