A quick glance at the specfile (after fixing the typo in the URL):
1. I would version the "Obsoletes:      oxygen-plasma-kde4".
2. Typo in oxygen-cursor-themes: "Obsoletes:      plasma-oxygen-common < 5.1.1.-2" – stray '.' before '-'.

Actually, as found by Dan Mossor on IRC, "Obsoletes:      oxygen-plasma-kde4" is entirely wrong, should be "Obsoletes:      plasma-oxygen-kde4 < some version" (the name is also wrong).

And as said on IRC (another upgrade path issue reported by Dan Mossor), the main (meta)package is missing, please add an empty "%files" list. (No %files list means no main package. An empty %files list means an empty main package. That's not the same.)

And please post updated "Spec URL" (s/oxygens/oxygen/) and especially "SRPM URL" links here.

Spec URL: https://dvratil.fedorapeople.org/plasma5/review/plasma-oxygen.spec
SRPM URL: https://dvratil.fedorapeople.org/plasma5/review/plasma-oxygen-5.1.1-6.fc20.src.rpm

Thanks for the comments.

- fixed the Obsoletes/Conflicts issue (hopefully)
- created empty %files section for main package

The Obsoletes are still wrong. Why "Obsoletes:      plasma-oxygen-kde4 < 5.1.1-1" in oxygen-cursor-themes and oxygen-sound-theme? This should be in qt4-style-oxygen instead of (or in addition to if you had shipped both names at some point in the past) your "Obsoletes:      oxygen-plasma-kde4". oxygen-cursor-themes and oxygen-sound-theme should have "Obsoletes:      plasma-oxygen-common < 5.1.1-1" instead, as they had in the first version of the specfile (but without the "5.1.1." typo ;-) ).

And you actually need to "Obsoletes:      plasma-oxygen-kde4 < 5.1.1-2", because you shipped a plasma-oxygen-kde4-5.1.1-1%{?dist}.

Spec URL: https://dvratil.fedorapeople.org/plasma5/review/plasma-oxygen.spec
SRPM URL: https://dvratil.fedorapeople.org/plasma5/review/plasma-oxygen-5.1.1-7.fc20.src.rpm

naming: ok
lots of subpkgs going on there, but it looks pretty good, upgrade paths are obviously tricky, but I think it's mostly sorted out now.

1. SHOULD remove from kwin-oxygen:
# Conflicts with kde-style-oxygen from kde-workspace
Conflicts:      kde-style-oxygen < 5.1.0-1
pretty sure this isn't true, and can be removed

2. SHOULD omit from qt4-style-oxygen and qt5-style-oxygen:
Requires: oxygen-cursor-themes = %{version}-%{release}
Requires: oxygen-sound-theme = %{version}-%{release}
I don't think these are needed, the widget style is/(should-be?) independent of cursor-theme and sounds

sources: ok
fc112c113dedcbac338e0db89af4b388  oxygen-5.1.1.tar.xz

macros: ok, though preferably
3. SHOULD use
make install/fast DESTDIR=%{buildroot}
rather than
%make_install

scriptlets: NOT OK
4. MUST add iconcache scriptlets to oxygen-cursor-themes subpkg

license: ok , but I think from licensecheck output we could bump to GPLv2+ if you want

Spec URL: https://dvratil.fedorapeople.org/plasma5/review/plasma-oxygen.spec
SRPM URL: https://dvratil.fedorapeople.org/plasma5/review/plasma-oxygen-5.1.1-8.fc20.src.rpm

- Remove Conflicts kde-style-oxygen from kwin-oxygen
- Remove Requires themes from qt{4,5}-style-oxygen
- Fixed scriptlets

Looks good, thanks, APPROVED

New Package SCM Request
=======================
Package Name: plasma-oxygen
Short Description: Plasma and Qt widget style and window decorations for PLasma 5 and KDE 4
Upstream URL: https://projects.kde.org/projects/kde/workspace/oxygen
Owners: dvratil ltinkl jgrulich kkofler rdieter than
Branches: f20 f21
InitialCC:

Git done (by process-git-requests).

I'll reset to modified since there aren't any (rawhide) builds yet