/usr/ is in ruby-serialport 1.3.1-1build3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/
/usr/lib/x86_64-linux-gnu/
/usr/lib/x86_64-linux-gnu/ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.3.0/
/usr/lib/x86_64-linux-gnu/ruby/vendor_ruby/2.3.0/serialport.so
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/serialport.rb
/usr/lib/ruby/vendor_ruby/serialport/
/usr/lib/ruby/vendor_ruby/serialport/version.rb
/usr/share/
/usr/share/rubygems-integration/
/usr/share/rubygems-integration/2.3.0/
/usr/share/rubygems-integration/2.3.0/specifications/
/usr/share/rubygems-integration/2.3.0/specifications/serialport-1.3.1.gemspec
/usr/share/doc/
/usr/share/doc/ruby-serialport/
/usr/share/doc/ruby-serialport/copyright
/usr/share/doc/ruby-serialport/changelog.Debian.gz