A map of Dorne after the restoration of peace under House Yronwood after the Council's War.
This is from an alternate ASoIaF history idea I've been kicking around, in which Prince Jaehaerys Targaryen (OTL Jaehaerys II) dies of a fever shortly before the disaster at Summerhall, where Aegon V and Prince Duncan die as IOTL. Succession is disputed between Aegon's grandson through Jaehaerys, Aerys, and Aegon's third son (the only information in the books so far about this son is that he existed). After a few minor military confrontations, a second Great Council is called to decide between them, and chooses Aerys. Whereas IOTL there was only one Great Council, ITTL the second GC makes itself and official organ of the government, with the power to choose the heir to the throne from among the deceased king's siblings and children.
Aerys was never fond of this provision, and after the death of two of his children he grows increasingly paranoid, believing that the Lords Paramount aim to destroy the Targaryen line. Being both cunning and irrational, he feigns mortal illness, and calls a third GC. When the Lords arrive, he turns his guards against them. Rickard Stark, Oberyn Martell (Doran died much younger, Oberyn is regent for his infant heir Myron), Luthor Tyrell, Hoster Tully, Jon Arryn, Balon Greyjoy, and Steffon Baratheon are all killed, but Tywin Lannister escapes. Aerys claims that the Lords attacked him, and Tywin claims that Aerys set a trap for the Lords. Tywin calls another GC, claiming the power to remove sitting kings, and crowns Rhaegar Targaryen in Lannisport. Rhaegar names him Hand of the King.
Aerys, seeing that all the Great Houses have turned on him, declares them all traitors and elevates various minor houses to fill their positions, including the powerful House Yronwood in Dorne. In most places, the Great Houses have good leadership and put down any such rebellions, but in Dorne there is a power void after the death of Oberyn. Elia Martell, married to Tywin's brother Tygett ITTL, calls for Dorne to rise against Aerys, and sails for Sunspear. The Lord/Prince Edgar Yronwood say that the whole war was set up as a gigantic power grab by Tywin, and accuse Elia of being a Lannister agent. A savage war breaks out, with the Yronwoods dominating the west and the Martells the east.
After a year of bloody stalemate in Dorne and of steady Rhaegar-faction advance in the rest of the country, King Aerys flees the capital in an armada with an army of thousands on board. He strikes nearly undefended Sunspear, sacking it and executing young Prince Myron. The Martell loyalists fight on, but Aerys and the Yronwoods now have a clear advantage. Castles and towns are sacked, and Elia flees from stronghold to stronghold. House Gargalen is completely destroyed for harboring her, and replaced with a mercenary leader working for Aerys. She flees into the desert, hoping to reach safety across the Red Mountains.
Meanwhile, Tywin and Rhaegar turn their forces against Dorne. The campaign has initial success, breaking into the valley of the Torrentine and forcing its way into Prince's Pass, but Dorne's natural defensive terrain makes progress difficult. An attempt to invade by sea ends in disaster off the Broken Arm, where Aerys' Royal Fleet destroys the combined Tyrell and Lannister fleets. Worse, Elia is caught only a few miles from safety, and burned to death by Aerys. The war rages on in the mountains for years. Three years after Elia's execution, Prince/Lord Ormond Yronwood breaks through the enemy lines and heads into the Marches, sacking castles along the way. He is eventually driven back to Dorne, and the war continues.
Eventually, both sides tire of war, and some Dornish houses are close to revolt against Aerys, whom they find dishonorable and suspicious. Meanwhile across the Red Mountains, Rhaegar has died in a hunting accident, leaving only one child, the sickly Aegon VI. The next-in-line for the throne is Lord Renlas Baratheon. Tywin Lannister meets Ormond Yronwood at Starfall to discuss peace, and they come to an agreement. Rhaegar will recognize Dornish independence, on the condition that Aerys and his son Viserys are turned over to the Lords Paramount for punishment. This suits Ormond fine, as he does not wish to share power with the unstable Targaryens. Tywin, meanwhile, wants to secure legitimacy for his line of Targaryens, and to have Prince Viserys to prevent Baratheon succession to the throne in case Aegon VI dies.
Aerys is taken by surprise by the Yronwood forces, and although one house calls for rebellion against the Yronwoods in the wake of the betrayal, the cry is not taken up and they change their minds at the sight of Prince Ormond's army. They are destroyed anyways, and their lands confiscated. Many houses grumble loudly afterwards, but none rebel. Aerys is delivered to Tywin at Horn Hill, close to a decade after his ill-conceived plot to destroy the Lords Paramount, and executed. Prince Viserys, however, dies along the way. The official reason given is sickness, but in fact he was poisoned by Ormond to weaken the Targaryen line and set the Seven Kingdoms on an unstable path.
Prince Ormond returns to Dorne. He grants himself the lands confiscated from Aerys and his supporters, as well as some strategic regions on the border. He rewards houses who supported him in the wars and in the deportation of Aerys, mostly by granting them land from the houses he is more suspicious of. Some of the houses losing land stage a brief revolt, but it goes nowhere. Because even Ormond has tired of bloodshed, they are not destroyed, but they do lose more land. A monument is erected in Planky Town to the restoration of peace to the country, and Ormond sets about creating a new bureaucracy and a stronger navy, as befits an independent state. Under the Yronwood Princes, Dorne will become a major commercial and military power in the southern Narrow Sea, and Planky Town will come to resemble the cities of Essos more than it does Maidenpool or Gulltown.