A good way to check whether a specific package is supported in your current layers is to search for it as follows:

$ cd /opt/yocto/fsl-community-bsp/sources
$ find -name "*busybox*"  

This will recursively search all layers for the BusyBox pattern. You can limit the search to recipes and append files by executing:

$ find -name "*busybox*.bb*" 

Yocto includes a bitbake-layers command-line utility that can also be used to search for specific recipes on the configured layers, with the preferred version appearing first:

$ bitbake-layers show-recipes "<package_name>" 

Here, <package_name> also supports wildcards.

For example:

$ bitbake-layers show-recipes gdb*
=== Matching recipes: ===
gdb:
  meta                 7.12.1
gdb-cross-arm:
  meta                 7.12.1
gdb-cross-canadian-arm:
  meta                 7.12.1
gdbm:
  meta                 1.12  

Finally, the devtool command-line utility can also be used to search the dependency cache with a regular expression. It will search on recipe or package names but also description and install files, so it is better suited in the context of developing recipes metadata:

$ devtool search <regular expression> 

To use devtool, the environment needs to be previously set up, and the shared state cache populated:

$ cd /opt/yocto/fsl-community-bsp
$ source setup-environment wandboard
$ bitbake <target-image>
$ devtool search gdb
Loaded 2323 entries from dependency cache.
perl                  Perl scripting language
shared-mime-info      Shared MIME type database and specification
bash-completion       Programmable Completion for Bash 4
glib-2.0              A general-purpose utility library
python                The Python Programming Language
gdbm                  Key/value database library with extensible hashing
gcc-runtime           Runtime libraries from GCC