In a lot of sources about goblins it says goblins can create cobbled item and in Goblins of Golarion it has rules on how they work. It sounds like the goblins can craft anything out of ‘garbage’ like weapon armor, cloths, back packs and any equipment.
So, I have a couple players playing goblin PCs. How should I handle the crafting of the cobbled items? Should I have them put skill point into craft(cobbling) or create a feat for crafting cobbling items?
Ah, Craft (Cobbling)... not to be confused with Profession (Cobbling) which is for repairing shoes. Yes, I'd require at least one rank in such a thing and allow it to apply to things like armor, weapons, and simple items. Obviously it shouldn't be used to make alchemical or magical items. Don't bother with a separate feat.
I'd just say let them 'pay' a fraction of the base item's cost (a quarter to half) to get/scrounge/barter for the 'trash' material. Whatever they make will have the permanent broken condition, unable to 'repair' it because that's as good as it gets.
Alternatively you could just halve the DCs for most crafting checks on what they want to make. Let them make it for free if they get up in arms for having to 'pay' for garbage components. Same broken condition applies. While it might be essentially free stuff at first, it won't be terribly useful at higher levels and nobody will want to buy it. Shouldn't be unbalancing and it'll let them have their fun. Let them specifically make dog-slicers and horse-choppers and let them give everything else they make fun little names.
The idea is to let them make cheaper, lower quality items with less difficulty. Hope that helps.